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Commit b5dd2422 authored by Olivier Deprez's avatar Olivier Deprez
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docs: spm design document refresh 



General refresh of the SPM document.

Change-Id: I2f8e37c3f34bc8511b115f00b9a53b6a6ff41bea
Signed-off-by: default avatarOlivier Deprez <olivier.deprez@arm.com>
parent 57dde212
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docs/components/secure-partition-manager.rst
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......@@ -6,6 +6,8 @@ Secure Partition Manager
Acronyms
========
+--------+-----------------------------------+
| CoT | Chain of Trust |
+--------+-----------------------------------+
| DMA | Direct Memory Access |
+--------+-----------------------------------+
......@@ -17,7 +19,7 @@ Acronyms
+--------+-----------------------------------+
| FIP | Firmware Image Package |
+--------+-----------------------------------+
| FF-A | Firmware Framework for A-class |
| FF-A | Firmware Framework for Armv8-A |
+--------+-----------------------------------+
| IPA | Intermediate Physical Address |
+--------+-----------------------------------+
......@@ -31,12 +33,16 @@ Acronyms
+--------+-----------------------------------+
| PE | Processing Element |
+--------+-----------------------------------+
| PM | Power Management |
+--------+-----------------------------------+
| PVM | Primary VM |
+--------+-----------------------------------+
| SMMU | System Memory Management Unit |
+--------+-----------------------------------+
| SP | Secure Partition |
+--------+-----------------------------------+
| SPD | Secure Payload Dispatcher |
+--------+-----------------------------------+
| SPM | Secure Partition Manager |
+--------+-----------------------------------+
| SPMC | SPM Core |
......@@ -59,111 +65,117 @@ Foreword
Two implementations of a Secure Partition Manager co-exist in the TF-A codebase:
- SPM based on the FF-A specification `[1]`_.
- SPM based on the MM interface to communicate with an S-EL0 partition `[2]`_.
- SPM based on the FF-A specification `[1]`_.
- SPM based on the MM interface to communicate with an S-EL0 partition `[2]`_.
Both implementations differ in their architectures and only one can be selected
at build time.
This document:
- describes the FF-A implementation where the Secure Partition Manager
resides at EL3 and S-EL2 (or EL3 and S-EL1).
- is not an architecture specification and it might provide assumptions
on sections mandated as implementation-defined in the specification.
- covers the implications to TF-A used as a bootloader, and Hafnium
used as a reference code base for an S-EL2 secure firmware on
platforms implementing Armv8.4-SecEL2.
- describes the FF-A implementation where the Secure Partition Manager
resides at EL3 and S-EL2 (or EL3 and S-EL1).
- is not an architecture specification and it might provide assumptions
on sections mandated as implementation-defined in the specification.
- covers the implications to TF-A used as a bootloader, and Hafnium
used as a reference code base for an S-EL2 secure firmware on
platforms implementing the FEAT_SEL2 (formerly Armv8.4 Secure EL2)
architecture extension.
Terminology
-----------
- Hypervisor refers to the NS-EL2 component managing Virtual Machines (or
partitions) in the Normal World.
- SPMC refers to the S-EL2 component managing Virtual Machines (or Secure
Partitions) in the Secure World when Armv8.4-SecEL2 extension is implemented.
- Alternatively, SPMC can refer to an S-EL1 component, itself being a Secure
Partition and implementing the FF-A ABI on pre-Armv8.4 platforms.
- VM refers to a Normal World Virtual Machine managed by an Hypervisor.
- SP refers to a Secure World "Virtual Machine" managed by the SPMC component.
- The term Hypervisor refers to the NS-EL2 component managing Virtual Machines
(or partitions) in the normal world.
- The term SPMC refers to the S-EL2 component managing secure partitions in
the secure world when the FEAT_SEL2 architecture extension is implemented.
- Alternatively, SPMC can refer to an S-EL1 component, itself being a secure
partition and implementing the FF-A ABI on platforms not implementing the
FEAT_SEL2 architecture extension.
- The term VM refers to a normal world Virtual Machine managed by an Hypervisor.
- The term SP refers to a secure world "Virtual Machine" managed by an SPMC.
Support for legacy platforms
----------------------------
In the implementation, the SPM is split into SPMD and SPMC components
(although not strictly mandated by the specification). SPMD is located
at EL3 and principally relays FF-A messages from NWd (Hypervisor or OS
kernel) to SPMC located either at S-EL1 or S-EL2.
In the implementation, the SPM is split into SPMD and SPMC components.
The SPMD is located at EL3 and mainly relays FF-A messages from
NWd (Hypervisor or OS kernel) to SPMC located either at S-EL1 or S-EL2.
Hence TF-A must support both cases where SPMC is either located at:
Hence TF-A supports both cases where the SPMC is located either at:
- S-EL1 supporting pre-Armv8.4 platforms. SPMD conveys FF-A protocol
from EL3 to S-EL1.
- S-EL2 supporting platforms implementing Armv8.4-SecEL2 extension.
SPMD conveys FF-A protocol from EL3 to S-EL2.
- S-EL1 supporting platforms not implementing the FEAT_SEL2 architecture
extension. The SPMD relays the FF-A protocol from EL3 to S-EL1.
- or S-EL2 supporting platforms implementing the FEAT_SEL2 architecture
extension. The SPMD relays the FF-A protocol from EL3 to S-EL2.
The same SPMD component is used to support both configurations. The SPMC
execution level is a build time choice.
The same TF-A SPMD component is used to support both configurations.
The SPMC exception level is a build time choice.
Sample reference stack
======================
The following diagram illustrates a possible configuration with SPMD and SPMC,
one or multiple Secure Partitions, with or without an optional Hypervisor:
The following diagram illustrates a possible configuration when the
FEAT_SEL2 architecture extension is implemented, showing the SPMD
and SPMC, one or multiple secure partitions, with an optional
Hypervisor:
.. image:: ../resources/diagrams/ff-a-spm-sel2.png
TF-A build options
==================
The following TF-A build options are provisioned:
- **SPD=spmd**: this option selects the SPMD component to relay FF-A
protocol from NWd to SWd back and forth. It is not possible to
enable another Secure Payload Dispatcher when this option is chosen.
- **SPMD_SPM_AT_SEL2**: this option adjusts the SPMC execution
level to being S-EL1 or S-EL2. It defaults to enabled (value 1) when
SPD=spmd is chosen.
- **CTX_INCLUDE_EL2_REGS**: this option permits saving (resp.
restoring) the EL2 system register context before entering (resp.
after leaving) the SPMC. It is mandatory when ``SPMD_SPM_AT_SEL2`` is
enabled. The context save/restore routine and exhaustive list of
registers is visible at `[4]`_.
- **SP_LAYOUT_FILE**: this option provides a text description file
providing paths to SP binary images and DTS format manifests
(see `Specifying partition binary image and DT`_). It
is required when ``SPMD_SPM_AT_SEL2`` is enabled hence when multiple
secure partitions are to be loaded on behalf of SPMC.
+------------------------------+----------------------+------------------+
| | CTX_INCLUDE_EL2_REGS | SPMD_SPM_AT_SEL2 |
+------------------------------+----------------------+------------------+
| SPMC at S-EL1 (e.g. OP-TEE) | 0 | 0 |
+------------------------------+----------------------+------------------+
| SPMC at S-EL2 (e.g. Hafnium) | 1 | 1 (default when |
| | | SPD=spmd) |
+------------------------------+----------------------+------------------+
This section explains the TF-A build options involved in building with
support for an FF-A based SPM where the SPMD is located at EL3 and the
SPMC located at S-EL1 or S-EL2:
- **SPD=spmd**: this option selects the SPMD component to relay the FF-A
protocol from NWd to SWd back and forth. It is not possible to
enable another Secure Payload Dispatcher when this option is chosen.
- **SPMD_SPM_AT_SEL2**: this option adjusts the SPMC exception
level to being S-EL1 or S-EL2. It defaults to enabled (value 1) when
SPD=spmd is chosen.
- **CTX_INCLUDE_EL2_REGS**: this option permits saving (resp.
restoring) the EL2 system register context before entering (resp.
after leaving) the SPMC. It is mandatorily enabled when
``SPMD_SPM_AT_SEL2`` is enabled. The context save/restore routine
and exhaustive list of registers is visible at `[4]`_.
- **SP_LAYOUT_FILE**: this option specifies a text description file
providing paths to SP binary images and manifests in DTS format
(see `Describing secure partitions`_). It
is required when ``SPMD_SPM_AT_SEL2`` is enabled hence when multiple
secure partitions are to be loaded on behalf of the SPMC.
+---------------+----------------------+------------------+
| | CTX_INCLUDE_EL2_REGS | SPMD_SPM_AT_SEL2 |
+---------------+----------------------+------------------+
| SPMC at S-EL1 | 0 | 0 |
+---------------+----------------------+------------------+
| SPMC at S-EL2 | 1 | 1 (default when |
| | | SPD=spmd) |
+---------------+----------------------+------------------+
Other combinations of such build options either break the build or are not
supported.
Note, the ``CTX_INCLUDE_EL2_REGS`` option provides the generic support for
barely saving/restoring EL2 registers from an Arm arch perspective. As such
it is decoupled from the ``SPD=spmd`` option.
BL32 option is re-purposed to specify the SPMC image. It can specify either the
Hafnium binary path (built for the secure world) or the path to a TEE binary
implementing the FF-A protocol.
BL33 option can specify either:
- the TFTF binary or
- the Hafnium binary path (built for the normal world) if VMs were loaded by
TF-A beforehand or
- a minimal loader performing the loading of VMs and Hafnium.
Notes:
- Only Arm's FVP platform is supported to use with the TF-A reference software
stack.
- The reference software stack uses FEAT_PAuth (formerly Armv8.3-PAuth) and
FEAT_BTI (formerly Armv8.5-BTI) architecture extensions by default at EL3
and S-EL2.
- The ``CTX_INCLUDE_EL2_REGS`` option provides the generic support for
barely saving/restoring EL2 registers from an Arm arch perspective. As such
it is decoupled from the ``SPD=spmd`` option.
- BL32 option is re-purposed to specify the SPMC image. It can specify either
the Hafnium binary path (built for the secure world) or the path to a TEE
binary implementing FF-A interfaces.
- BL33 option can specify the TFTF binary or a normal world loader
such as U-Boot or the UEFI framework.
Sample TF-A build command line when SPMC is located at S-EL1
(typically pre-Armv8.4):
(e.g. when the FEAT_EL2 architecture extension is not implemented):
.. code:: shell
......@@ -172,67 +184,108 @@ Sample TF-A build command line when SPMC is located at S-EL1
SPD=spmd \
SPMD_SPM_AT_SEL2=0 \
BL32=<path-to-tee-binary> \
BL33=<path-to-nwd-binary> \
BL33=<path-to-bl33-binary> \
PLAT=fvp \
all fip
Sample TF-A build command line for an Armv8.4-SecEL2 enabled system
where SPMC is located at S-EL2:
Sample TF-A build command line for a FEAT_SEL2 enabled system where the SPMC is
located at S-EL2:
.. code:: shell
make \
CROSS_COMPILE=aarch64-none-elf- \
PLAT=fvp \
SPD=spmd \
CTX_INCLUDE_EL2_REGS=1 \
ARM_ARCH_MINOR=4 \
BL32=<path-to-swd-hafnium-binary>
BL33=<path-to-nwd-binary> \
ARM_ARCH_MINOR=5 \
BRANCH_PROTECTION=1 \
CTX_INCLUDE_PAUTH_REGS=1 \
BL32=<path-to-hafnium-binary> \
BL33=<path-to-bl33-binary> \
SP_LAYOUT_FILE=sp_layout.json \
PLAT=fvp \
all fip
Build options to enable secure boot:
Same as above with enabling secure boot in addition:
.. code:: shell
make \
CROSS_COMPILE=aarch64-none-elf- \
PLAT=fvp \
SPD=spmd \
CTX_INCLUDE_EL2_REGS=1 \
ARM_ARCH_MINOR=4 \
BL32=<path-to-swd-hafnium-binary>
BL33=<path-to-nwd-binary> \
SP_LAYOUT_FILE=../tf-a-tests/build/fvp/debug/sp_layout.json \
ARM_ARCH_MINOR=5 \
BRANCH_PROTECTION=1 \
CTX_INCLUDE_PAUTH_REGS=1 \
BL32=<path-to-hafnium-binary> \
BL33=<path-to-bl33-binary> \
SP_LAYOUT_FILE=sp_layout.json \
MBEDTLS_DIR=<path-to-mbedtls-lib> \
TRUSTED_BOARD_BOOT=1 \
COT=dualroot \
ARM_ROTPK_LOCATION=devel_rsa \
ROT_KEY=plat/arm/board/common/rotpk/arm_rotprivk_rsa.pem \
GENERATE_COT=1 \
PLAT=fvp \
all fip
FVP model invocation
====================
The FVP command line needs the following options to exercise the S-EL2 SPMC:
+---------------------------------------------------+------------------------------------+
| - cluster0.has_arm_v8-5=1 | Implements FEAT_SEL2, FEAT_PAuth, |
| - cluster1.has_arm_v8-5=1 | and FEAT_BTI. |
+---------------------------------------------------+------------------------------------+
| - pci.pci_smmuv3.mmu.SMMU_AIDR=2 | Parameters required for the |
| - pci.pci_smmuv3.mmu.SMMU_IDR0=0x0046123B | SMMUv3.2 modeling. |
| - pci.pci_smmuv3.mmu.SMMU_IDR1=0x00600002 | |
| - pci.pci_smmuv3.mmu.SMMU_IDR3=0x1714 | |
| - pci.pci_smmuv3.mmu.SMMU_IDR5=0xFFFF0472 | |
| - pci.pci_smmuv3.mmu.SMMU_S_IDR1=0xA0000002 | |
| - pci.pci_smmuv3.mmu.SMMU_S_IDR2=0 | |
| - pci.pci_smmuv3.mmu.SMMU_S_IDR3=0 | |
+---------------------------------------------------+------------------------------------+
| - cluster0.has_branch_target_exception=1 | Implements FEAT_BTI. |
| - cluster1.has_branch_target_exception=1 | |
+---------------------------------------------------+------------------------------------+
| - cluster0.restriction_on_speculative_execution=2 | Required by the EL2 context |
| - cluster1.restriction_on_speculative_execution=2 | save/restore routine. |
+---------------------------------------------------+------------------------------------+
Sample FVP command line invocation:
.. code:: shell
<path-to-fvp-model>/FVP_Base_RevC-2xAEMv8A -C pctl.startup=0.0.0.0
-C cluster0.NUM_CORES=4 -C cluster1.NUM_CORES=4 -C bp.secure_memory=1 \
-C bp.secureflashloader.fname=trusted-firmware-a/build/fvp/debug/bl1.bin \
-C bp.flashloader0.fname=trusted-firmware-a/build/fvp/debug/fip.bin \
-C bp.pl011_uart0.out_file=fvp-uart0.log -C bp.pl011_uart1.out_file=fvp-uart1.log \
-C bp.pl011_uart2.out_file=fvp-uart2.log \
-C cluster0.has_arm_v8-5=1 -C cluster1.has_arm_v8-5=1 -C pci.pci_smmuv3.mmu.SMMU_AIDR=2 \
-C pci.pci_smmuv3.mmu.SMMU_IDR0=0x0046123B -C pci.pci_smmuv3.mmu.SMMU_IDR1=0x00600002 \
-C pci.pci_smmuv3.mmu.SMMU_IDR3=0x1714 -C pci.pci_smmuv3.mmu.SMMU_IDR5=0xFFFF0472 \
-C pci.pci_smmuv3.mmu.SMMU_S_IDR1=0xA0000002 -C pci.pci_smmuv3.mmu.SMMU_S_IDR2=0 \
-C pci.pci_smmuv3.mmu.SMMU_S_IDR3=0 \
-C cluster0.has_branch_target_exception=1 \
-C cluster1.has_branch_target_exception=1 \
-C cluster0.restriction_on_speculative_execution=2 \
-C cluster1.restriction_on_speculative_execution=2
Boot process
============
Loading Hafnium and Secure Partitions in the secure world
Loading Hafnium and secure partitions in the secure world
---------------------------------------------------------
The Hafnium implementation in normal world requires VMs to be loaded in
memory prior to booting. The mechanism upon which VMs are loaded and
exposed to Hafnium are either:
TF-A BL2 is the bootlader for the SPMC and SPs in the secure world.
- by supplying a ramdisk image where VM images are concatenated (1)
- or by providing VM load addresses within Hafnium manifest (2)
TF-A is the bootlader for the Hafnium and SPs in the secure world. TF-A
does not provide tooling or libraries manipulating ramdisks as required
by (1). Thus BL2 loads SPs payloads independently.
SPs may be signed by different parties (SiP, OEM/ODM, TOS vendor, etc.).
Thus they are supplied as distinct “self-contained” signed entities within
the FIP flash image. The FIP image itself is not signed hence providing
ability to upgrade SPs in the field.
Thus they are supplied as distinct signed entities within the FIP flash
image. The FIP image itself is not signed hence this provides the ability
to upgrade SPs in the field.
Booting through TF-A
--------------------
......@@ -241,26 +294,27 @@ SP manifests
~~~~~~~~~~~~
An SP manifest describes SP attributes as defined in `[1]`_
section 3.1 (partition manifest at virtual FF-A instance) in DTS text format. It
is represented as a single file associated with the SP. A sample is
(partition manifest at virtual FF-A instance) in DTS format. It is
represented as a single file associated with the SP. A sample is
provided by `[5]`_. A binding document is provided by `[6]`_.
Secure Partition packages
~~~~~~~~~~~~~~~~~~~~~~~~~
Secure Partitions are bundled as independent package files consisting
Secure partitions are bundled as independent package files consisting
of:
- a header
- a DTB
- an image payload
- a header
- a DTB
- an image payload
The header starts with a magic value and offset values to SP DTB and
image payload. Each SP package is loaded independently by BL2 loader
and verified for authenticity and integrity.
The SP package identified by its UUID (matching FF-A uuid) is inserted
as a single entry into the FIP at end of the TF-A build flow as shown:
The SP package identified by its UUID (matching FF-A uuid property) is
inserted as a single entry into the FIP at end of the TF-A build flow
as shown:
.. code:: shell
......@@ -278,18 +332,17 @@ as a single entry into the FIP at end of the TF-A build flow as shown:
.. uml:: ../resources/diagrams/plantuml/fip-secure-partitions.puml
Specifying partition binary image and DT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Describing secure partitions
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A description file (json format) is passed to the build flow specifying
paths to the SP binary image and associated DTS partition manifest file.
The latter is going through the dtc compiler to generate the dtb fed into
the SP package.
This file also specifies the owner of the SP, which is an optional field and
identifies the signing domain in case of dualroot CoT.
The possible owner of an SP could either be Silicon Provider or Platform, and
the corresponding "owner" field value could either be "SiP" or "Plat".
In absence of "owner" field, it defaults to "SiP".
A json-formatted description file is passed to the build flow specifying paths
to the SP binary image and associated DTS partition manifest file. The latter
is processed by the dtc compiler to generate a DTB fed into the SP package.
This file also specifies the SP owner (as an optional field) identifying the
signing domain in case of dual root CoT.
The SP owner can either be the silicon or the platform provider. The
corresponding "owner" field value can either take the value of "SiP" or "Plat".
In absence of "owner" field, it defaults to "SiP" owner.
.. code:: shell
......@@ -310,14 +363,16 @@ In absence of "owner" field, it defaults to "SiP".
SPMC manifest
~~~~~~~~~~~~~
This manifest contains an SPMC attributes node consumed by SPMD at boot time. It
is implementing the description from `[1]`_ section 3.2 (SP manifest at physical
FF-A instance). The SP manifest at physical FF-A instance is used by the SPMD to
setup a SP that co-resides with the SPMC and executes at S-EL1 or Secure
Supervisor mode.
This manifest contains the SPMC *attribute* node consumed by the SPMD at boot
time. It implements `[1]`_ (SP manifest at physical FF-A instance) and serves
two different cases:
In this implementation its usage is extended to the secure physical FF-A
instance where SPMC executes at S-EL2.
- The SPMC resides at S-EL1: the SPMC manifest is used by the SPMD to setup a
SP that co-resides with the SPMC and executes at S-EL1 or Secure Supervisor
mode.
- The SPMC resides at S-EL2: the SPMC manifest is used by the SPMD to setup
the environment required by the SPMC to run at S-EL2. SPs run at S-EL1 or
S-EL0.
.. code:: shell
......@@ -331,28 +386,28 @@ instance where SPMC executes at S-EL2.
binary_size = <0x60000>;
};
- *spmc_id* defines the endpoint ID value that SPMC can query through
``FFA_ID_GET``.
- *maj_ver/min_ver*. SPMD checks provided version versus its internal
version and aborts if not matching.
- *exec_state* defines SPMC execution state (can be AArch64 for
Hafnium, or AArch64/AArch32 for OP-TEE at S-EL1).
- *load_address* and *binary_size* are mostly used to verify secondary
entry points fit into the loaded binary image.
- *entrypoint* defines the cold boot primary core entry point used by
SPMD (currently matches ``BL32_BASE``)
- *spmc_id* defines the endpoint ID value that SPMC can query through
``FFA_ID_GET``.
- *maj_ver/min_ver*. SPMD checks provided version versus its internal
version and aborts if not matching.
- *exec_state* defines the SPMC execution state (AArch64 or AArch32).
Notice Hafnium used as a SPMC only supports AArch64.
- *load_address* and *binary_size* are mostly used to verify secondary
entry points fit into the loaded binary image.
- *entrypoint* defines the cold boot primary core entry point used by
SPMD (currently matches ``BL32_BASE``) to enter the SPMC.
Other nodes in the manifest are consumed by Hafnium in the secure world.
A sample can be found at [7]:
- The *chosen* node is currently unused in SWd. It is meant for NWd to
specify the init ramdisk image.
- The *hypervisor* node describes SPs. *is_ffa_partition* boolean
attribute indicates an SP. Load-addr field specifies the load address
at which TF-A loaded the SP package.
- *cpus* node provide the platform topology and allows MPIDR to VMPIDR
mapping. Notice with current implementation primary cpu is declared
first, then secondary cpus must be declared in reverse order.
- The *hypervisor* node describes SPs. *is_ffa_partition* boolean attribute
indicates a FF-A compliant SP. The *load_address* field specifies the load
address at which TF-A loaded the SP package.
- *cpus* node provide the platform topology and allows MPIDR to VMPIDR mapping.
Note the primary core is declared first, then secondary core are declared
in reverse order.
- The *memory* node provides platform information on the ranges of memory
available to the SPMC.
SPMC boot
~~~~~~~~~
......@@ -363,134 +418,111 @@ The SPMC manifest is loaded by BL2 as the ``TOS_FW_CONFIG`` image.
BL2 passes the SPMC manifest address to BL31 through a register.
BL31(SPMD) runs from primary core, initializes the core contexts and
launches BL32 passing the SPMC manifest address through a register.
At boot time, the SPMD in BL31 runs from the primary core, initializes the core
contexts and launches the SPMC (BL32) passing the SPMC manifest address through
a register.
Loading of SPs
~~~~~~~~~~~~~~
.. uml:: ../resources/diagrams/plantuml/bl2-loading-sp.puml
At boot time, BL2 loads SPs sequentially in addition to the SPMC as depicted
below:
.. uml:: ../resources/diagrams/plantuml/bl2-loading-sp.puml
Notice this boot flow is an implementation sample on Arm's FVP platform. Platforms
not using FW_CONFIG would adjust to a different implementation.
Note this boot flow is an implementation sample on Arm's FVP platform.
Platforms not using TF-A's *Firmware CONFiguration* framework would adjust to a
different implementation.
Secure boot
~~~~~~~~~~~
The SP content certificate is inserted as a separate FIP item so that BL2 loads SPMC,
SPMC manifest and Secure Partitions and verifies them for authenticity and integrity.
SPMC manifest, secure partitions and verifies them for authenticity and integrity.
Refer to TBBR specification `[3]`_.
The multiple-signing domain feature (in current state dual signing domain) allows
the use of two root keys namely S-ROTPK and NS-ROTPK (see `[8]`_):
The multiple-signing domain feature (in current state dual signing domain `[8]`_) allows
the use of two root keys namely S-ROTPK and NS-ROTPK:
- SPMC (BL32) and SPMC manifest are signed by the SiP using the S-ROTPK.
- BL33 may be signed by the OEM using NS-ROTPK.
- An SP may be signed either by SiP (using S-ROTPK) or by OEM (using NS-ROTPK).
- SPMC (BL32) and SPMC manifest are signed by the SiP using the S-ROTPK.
- BL33 may be signed by the OEM using NS-ROTPK.
- An SP may be signed either by SiP (using S-ROTPK) or by OEM (using NS-ROTPK).
Longer term multiple signing domain will allow additional signing keys, e.g.
if SPs originate from different parties.
See `TF-A build options`_ for a sample build command line.
Also refer to `Describing secure partitions`_ and `TF-A build options`_ sections.
Hafnium in the secure world
===========================
**NOTE: this section is work in progress. Descriptions and implementation choices
are subject to evolve.**
General considerations
----------------------
Build platform for the secure world
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The implementation might add specific code parts only relevant to the
secure world. Such code parts might be isolated into different files
and/or conditional code enclosed by a ``SECURE_WORLD`` macro.
In the Hafnium reference implementation specific code parts are only relevant to
the secure world. Such portions are isolated in architecture specific files
and/or enclosed by a ``SECURE_WORLD`` macro.
Secure Partitions CPU scheduling
Secure partitions CPU scheduling
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In the normal world, VMs are scheduled by the FFA_RUN ABI invoked from the
primary scheduler (in the primary VM), or by a direct message request or
response.
The FF-A v1.0 specification `[1]`_ provides two ways to relinquinsh CPU time to
secure partitions. For this a VM (Hypervisor or OS kernel), or SP invokes one of:
With the FF-A EAC specification, Secure Partitions are scheduled by direct
message invocations from a NWd VM or another SP.
- the FFA_MSG_SEND_DIRECT_REQ interface.
- the FFA_RUN interface.
Platform topology
~~~~~~~~~~~~~~~~~
As stated in `[1]`_ section 4.4.1 the SPMC implementation assumes the
The *execution-ctx-count* SP manifest field can take the value of one or the
total number of PEs. The FF-A v1.0 specification `[1]`_ recommends the
following SP types:
- Pinned MP SPs: an Execution Context id matches a physical PE id. MP
SPs must implement the same number of ECs as the number of PEs in the
platform. Hence the *execution-ctx-count* as defined by
`[1]`_ (or NWd-Hafnium *vcpu_count*) can only take the
value of one or the number of physical PEs.
- Migratable UP SPs: a single execution context can run and be migrated
on any physical PE. It declares a single EC in its SP manifest. An UP
SP can receive a direct message request on any physical core.
Usage of PSCI services in the secure world
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- The normal world Hypervisor (optional) or OS kernel issues PSCI service
invocations e.g. to request PSCI version, wake-up a secondary core, or request
core suspend. This happens at the non-secure physical FF-A instance. In the
example case of Hafnium in the normal world, it boots on the primary core and
one of the first initialization step is to request the PSCI version. It then
launches the primary VM. The primary VM upon initializing performs PSCI service
calls (at non-secure virtual FF-A instance) which are trapped by the
Hypervisor. Invocation from OS Kernel ends straight at EL3. The PVM issues
``PSCI_CPU_ON`` service calls to wake-up secondary cores by passing an
``MPIDR``, entry point address and a CPU context address. The EL3 PSCI layer
then performs an exception return to the secondary core entry point on the
targeted core. Other PSCI calls can happen at run-time from the PVM e.g. to
request core suspend.
- In the existing TF-A PSCI standard library, PSCI service calls are filtered at
EL3 to only originate from the NWd. Thus concerning the SPMC (at secure
physical FF-A instance) the PSCI service invocations cannot happen as in the
normal world. For example, a ``PSCI_CPU_ON`` service invocation from the SPMC
does not reach the PSCI layer.
- Pinned MP SPs: an execution context matches a physical PE. MP SPs must
implement the same number of ECs as the number of PEs in the platform.
- Migratable UP SPs: a single execution context can run and be migrated on any
physical PE. Such SP declares a single EC in its SP manifest. An UP SP can
receive a direct message request originating from any physical core targeting
the single execution context.
Parsing SP partition manifests
------------------------------
Hafnium must be able to consume SP manifests as defined in
`[1]`_ section 3.1, at least for the mandatory fields.
Hafnium consumes SP manifests as defined in `[1]`_ and `SP manifests`_.
Note the current implementation may not implement all optional fields.
The SP manifest may contain memory and device regions nodes.
The SP manifest may contain memory and device regions nodes. In case of
an S-EL2 SPMC:
- Memory regions shall be mapped in the SP Stage-2 translation regime at
load time. A memory region node can specify RX/TX buffer regions in which
case it is not necessary for an SP to explicitly call the ``FFA_RXTX_MAP``
service.
- Device regions shall be mapped in SP Stage-2 translation regime as
peripherals and possibly allocate additional resources (e.g. interrupts)
- Memory regions are mapped in the SP EL1&0 Stage-2 translation regime at
load time (or EL1&0 Stage-1 for an S-EL1 SPMC). A memory region node can
specify RX/TX buffer regions in which case it is not necessary for an SP
to explicitly invoke the ``FFA_RXTX_MAP`` interface.
- Device regions are mapped in the SP EL1&0 Stage-2 translation regime (or
EL1&0 Stage-1 for an S-EL1 SPMC) as peripherals and possibly allocate
additional resources (e.g. interrupts).
Base addresses for memory and device region nodes are IPAs provided SPMC
identity maps IPAs to PAs within SP Stage-2 translation regime.
For the S-EL2 SPMC, base addresses for memory and device region nodes are IPAs
provided the SPMC identity maps IPAs to PAs within SP EL1&0 Stage-2 translation
regime.
Note: currently both VTTBR_EL2 and VSTTBR_EL2 resolve to the same set of page
tables. It is still open whether two sets of page tables shall be provided per
SP. The memory region node as defined in the spec (section 3.1 Table 10)
Note: in the current implementation both VTTBR_EL2 and VSTTBR_EL2 point to the
same set of page tables. It is still open whether two sets of page tables shall
be provided per SP. The memory region node as defined in the specification
provides a memory security attribute hinting to map either to the secure or
non-secure stage-2 table.
non-secure EL1&0 Stage-2 table if it exists.
Passing boot data to the SP
---------------------------
`[1]`_ Section 3.4.2 “Protocol for passing data” defines a
method to passing boot data to SPs (not currently implemented).
In `[1]`_ , the "Protocol for passing data" section defines a method for passing
boot data to SPs (not currently implemented).
Provided that the whole Secure Partition package image (see `Secure
Partition packages`_) is mapped to the SP's secure Stage-2 translation
regime, an SP can access its own manifest DTB blob and extract its partition
manifest properties.
Provided that the whole secure partition package image (see
`Secure Partition packages`_) is mapped to the SP secure EL1&0 Stage-2
translation regime, an SP can access its own manifest DTB blob and extract its
partition manifest properties.
SP Boot order
-------------
......@@ -499,343 +531,284 @@ SP manifests provide an optional boot order attribute meant to resolve
dependencies such as an SP providing a service required to properly boot
another SP.
It is possible for an SP to call into another SP through a direct request
provided the latter SP has already been booted.
Boot phases
-----------
Primary core boot-up
~~~~~~~~~~~~~~~~~~~~
The SPMC performs its platform initializations then loads and creates
secure partitions based on SP packages and manifests. Then each secure
partition is launched in sequence (see `SP Boot order`_) on their primary
Execution Context.
Notice the primary physical core may not be core 0. Hence if the primary
core linear id is N, the 1:1 mapping requires MP SPs are launched using
EC[N] on PE[N] (see `Platform topology`_).
The SP's primary Execution Context (or the EC used when the partition is booted)
exits through ``FFA_MSG_WAIT`` to indicate successful initialization.
Secondary physical core boot-up
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Upon boot-up, the SPMC running on the primary core performs
implementation-defined SPMD service calls at secure physical FF-A instance
to register the secondary physical cores entry points and context information:
- This is done through a direct message request invocation to the SPMD
(``SET_ENTRY_POINT``). This service call does not wake-up the targeted
core immediately. The secondary core is woken up later by a NWd
``PSCI_CPU_ON`` service invocation. A notification is passed from EL3
PSCI layer to the SPMD, and then to SPMC through an implementation-defined
interface.
- The SPMC/SPMD interface can consist of FF-A direct message requests/responses
transporting PM events.
If there is no Hypervisor in the normal world, the OS Kernel issues
``PSCI_CPU_ON`` calls that are directly trapped to EL3.
When a secondary physical core wakes-up the SPMD notifies the SPMC which updates
its internal states reflecting current physical core is being turned on.
It might then return straight to the SPMD and then to the NWd.
*(under discussion)* There may be possibility that an SP registers "PM events"
(during primary EC boot stage) through an ad-hoc interface. Such events would
be relayed by SPMC to one or more registered SPs on need basis
(see `Power management`_).
Secondary virtual core boot-up
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In the example case where Hafnium exists in the normal world, secondary VMs
issue a ``PSCI_CPU_ON`` service call which is trapped to the Hypervisor. The
latter then enables the vCPU context for the targeted core, and switches to
the PVM down to the kernel driver with an ``HF_WAKE_UP`` message. The NWd
driver in PVM can then schedule the newly woken up vCPU context.
In the secure world the primary EC of a given SP passes the secondary EC entry
point and context. The SMC service call is trapped into the SPMC. This can be
either *(under discussion)*:
- a specific interface registering the secondary EC entry point,
similarly to above ``SET_ENTRY_POINT`` service.
- Re-purposing the ``PSCI_CPU_ON`` function id. It is
assumed that even if the input arguments are the same as the ones defined in
the PSCI standard, the usage deviates by the fact the secondary EC is not
woken up immediately. At least for the FF-A EAC where only
direct messaging is allowed, it is only after the first direct
message invocation that the secondary EC is entered. This option
might be preferred when the same code base is re-used for a VM or
an SP. The ABI to wake-up a secondary EC can remain similar.
SPs are always scheduled from the NWd, this paradigm did not change from legacy
TEEs. There must always be some logic (or driver) in the NWd to relinquish CPU
cycles to the SWd. If primary core is 0, an SP EC[x>0] entry point is supplied
by the SP EC[0] when the system boots in SWd. But this EC[x] is not immediately
entered at boot. Later in the boot process when NWd is up, a direct message
request issued from physical core 1 ends up in SP EC[1], and only at this stage
this context is effectively scheduled.
It should be possible for an SP to call into another SP through direct message
provided the latter SP has been booted already. The "boot-order" field in
partition manifests (`SP Boot order`_) fulfills the dependency towards availability
of a service within an SP offered to another SP.
Upon boot-up, BL31 hands over to the SPMC (BL32) on the primary boot physical
core. The SPMC performs its platform initializations and registers the SPMC
secondary physical core entry point physical address by the use of the
FFA_SECONDARY_EP_REGISTER interface (SMC invocation from the SPMC to the SPMD
at secure physical FF-A instance). This interface is implementation-defined in
context of FF-A v1.0.
The SPMC then creates secure partitions based on SP packages and manifests. Each
secure partition is launched in sequence (`SP Boot order`_) on their "primary"
execution context. If the primary boot physical core linear id is N, an MP SP is
started using EC[N] on PE[N] (see `Platform topology`_). If the partition is a
UP SP, it is started using its unique EC0 on PE[N].
The SP primary EC (or the EC used when the partition is booted as described
above):
- Performs the overall SP boot time initialization, and in case of a MP SP,
prepares the SP environment for other execution contexts.
- In the case of a MP SP, it invokes the FFA_SECONDARY_EP_REGISTER at secure
virtual FF-A instance (SMC invocation from SP to SPMC) to provide the IPA
entry point for other execution contexts.
- Exits through ``FFA_MSG_WAIT`` to indicate successful initialization or
``FFA_ERROR`` in case of failure.
Secondary cores boot-up
~~~~~~~~~~~~~~~~~~~~~~~
Once the system is started and NWd brought up, a secondary physical core is
woken up by the ``PSCI_CPU_ON`` service invocation. The TF-A SPD hook mechanism
calls into the SPMD on the newly woken up physical core. Then the SPMC is
entered at the secondary physical core entry point.
In the current implementation, the first SP is resumed on the coresponding EC
(the virtual CPU which matches the physical core). The implication is that the
first SP must be a MP SP.
In a linux based system, once secure and normal worlds are booted but prior to
a NWd FF-A driver has been loaded:
- The first SP has initialized all its ECs in response to primary core boot up
(at system initialization) and secondary core boot up (as a result of linux
invoking PSCI_CPU_ON for all secondary cores).
- Other SPs have their first execution context initialized as a result of secure
world initialization on the primary boot core. Other ECs for those SPs have to
be run first through ffa_run to complete their initialization (which results
in the EC completing with FFA_MSG_WAIT).
Refer to `Power management`_ for further details.
Mandatory interfaces
--------------------
The following interfaces must be exposed to any VM or SP:
The following interfaces are exposed to SPs:
- ``FFA_STATUS``
- ``FFA_ERROR``
- ``FFA_INTERRUPT``
- ``FFA_VERSION``
- ``FFA_FEATURES``
- ``FFA_RX_RELEASE``
- ``FFA_RXTX_MAP``
- ``FFA_RXTX_UNMAP``
- ``FFA_RXTX_UNMAP`` (not implemented)
- ``FFA_PARTITION_INFO_GET``
- ``FFA_ID_GET``
- ``FFA_MSG_WAIT``
- ``FFA_MSG_SEND_DIRECT_REQ``
- ``FFA_MSG_SEND_DIRECT_RESP``
- ``FFA_MEM_DONATE``
- ``FFA_MEM_LEND``
- ``FFA_MEM_SHARE``
- ``FFA_MEM_RETRIEVE_REQ``
- ``FFA_MEM_RETRIEVE_RESP``
- ``FFA_MEM_RELINQUISH``
- ``FFA_MEM_RECLAIM``
- ``FFA_SECONDARY_EP_REGISTER``
FFA_VERSION
~~~~~~~~~~~
Per `[1]`_ section 8.1 ``FFA_VERSION`` requires a
*requested_version* parameter from the caller.
``FFA_VERSION`` requires a *requested_version* parameter from the caller.
The returned value depends on the caller:
In the current implementation when ``FFA_VERSION`` is invoked from:
- Hypervisor in NS-EL2: the SPMD returns the SPMC version specified
in the SPMC manifest.
- OS kernel in NS-EL1 when NS-EL2 is not present: the SPMD returns the
SPMC version specified in the SPMC manifest.
- VM in NWd: the Hypervisor returns its implemented version.
- SP in SWd: the SPMC returns its implemented version.
- SPMC at S-EL1/S-EL2: the SPMD returns its implemented version.
- Hypervisor or OS kernel in NS-EL1/EL2: the SPMD returns the SPMC version
specified in the SPMC manifest.
- SP: the SPMC returns its own implemented version.
- SPMC at S-EL1/S-EL2: the SPMD returns its own implemented version.
FFA_FEATURES
~~~~~~~~~~~~
FF-A features may be discovered by Secure Partitions while booting
through the SPMC. However, SPMC cannot get features from Hypervisor
early at boot time as NS world is not setup yet.
FF-A features supported by the SPMC may be discovered by secure partitions at
boot (that is prior to NWd is booted) or run-time.
The SPMC calling FFA_FEATURES at secure physical FF-A instance always get
FFA_SUCCESS from the SPMD.
The Hypervisor may decide to gather FF-A features from SPMC through SPMD
once at boot time and store the result. Later when a VM requests FF-A
features, the Hypervisor can adjust its own set of features with what
SPMC advertised, if necessary. Another approach is to always forward FF-A
features to the SPMC when a VM requests it to the Hypervisor. Although
the result is not supposed to change over time so there may not be added
value doing the systematic forwarding.
The request made by an Hypervisor or OS kernel is forwarded to the SPMC and
the response relayed back to the NWd.
FFA_RXTX_MAP/FFA_RXTX_UNMAP
~~~~~~~~~~~~~~~~~~~~~~~~~~~
VM mailboxes are re-purposed to serve as SP RX/TX buffers. The RX/TX
map API maps the send and receive buffer IPAs to the SP Stage-2 translation regime.
When invoked from a secure partition FFA_RXTX_MAP maps the provided send and
receive buffers described by their IPAs to the SP EL1&0 Stage-2 translation
regime as secure buffers in the MMU descriptors.
Hafnium in the normal world defines VMs and their attributes as logical structures,
including a mailbox used for FF-A indirect messaging, memory sharing, or the
`FFA_PARTITION_INFO_GET`_ ABI.
This same mailbox structure is re-used in the SPMC. `[1]`_ states only direct
messaging is allowed to SPs. Thus mailbox usage is restricted to implementing
`FFA_PARTITION_INFO_GET`_ and memory sharing ABIs.
When invoked from the Hypervisor or OS kernel, the buffers are mapped into the
SPMC EL2 Stage-1 translation regime and marked as NS buffers in the MMU
descriptors.
Note:
- FFA_RXTX_UNMAP is not implemented.
FFA_PARTITION_INFO_GET
~~~~~~~~~~~~~~~~~~~~~~
Partition info get service call can originate:
- from SP to SPM
- from VM to Hypervisor
- from Hypervisor to SPM
Partition info get call can originate:
For the latter case, the service call must be forwarded through the SPMD.
- from SP to SPMC
- from Hypervisor or OS kernel to SPMC. The request is relayed by the SPMD.
FFA_ID_GET
~~~~~~~~~~
The SPMD returns:
The FF-A id space is split into a non-secure space and secure space:
- a default zero value on invocation from the Hypervisor.
- The ``spmc_id`` value specified in the SPMC manifest on invocation from
the SPMC (see `SPMC manifest`_)
- FF-A ID with bit 15 clear relates to VMs.
- FF-A ID with bit 15 set related to SPs.
- FF-A IDs 0, 0xffff, 0x8000 are assigned respectively to the Hypervisor, SPMD
and SPMC.
The FF-A id space is split into a non-secure space and secure space:
The SPMD returns:
- FF-A id with bit 15 clear refer to normal world VMs.
- FF-A id with bit 15 set refer to secure world SPs
- The default zero value on invocation from the Hypervisor.
- The ``spmc_id`` value specified in the SPMC manifest on invocation from
the SPMC (see `SPMC manifest`_)
Such convention helps the SPMC discriminating the origin and destination worlds
in an FF-A service invocation. In particular the SPMC shall filter unauthorized
This convention helps the SPMC to determine the origin and destination worlds in
an FF-A ABI invocation. In particular the SPMC shall filter unauthorized
transactions in its world switch routine. It must not be permitted for a VM to
use a secure FF-A id as origin world through spoofing:
use a secure FF-A ID as origin world by spoofing:
- A VM-to-SP messaging passing shall have an origin world being non-secure
(FF-A id bit 15 clear) and destination world being secure (FF-A id bit 15
set).
- Similarly, an SP-to-SP message shall have FF-A id bit 15 set for both origin
and destination ids.
- A VM-to-SP direct request/response shall set the origin world to be non-secure
(FF-A ID bit 15 clear) and destination world to be secure (FF-A ID bit 15
set).
- Similarly, an SP-to-SP direct request/response shall set the FF-A ID bit 15
for both origin and destination IDs.
An incoming direct message request arriving at SPMD from NWd is forwarded to
SPMC without a specific check. The SPMC is resumed through eret and "knows" the
message is coming from normal world in this specific code path. Thus the origin
endpoint id must be checked by SPMC for being a normal world id.
endpoint ID must be checked by SPMC for being a normal world ID.
An SP sending a direct message request must have bit 15 set in its origin
endpoint id and this can be checked by the SPMC when the SP invokes the ABI.
endpoint ID and this can be checked by the SPMC when the SP invokes the ABI.
The SPMC shall reject the direct message if the claimed world in origin endpoint
id is not consistent:
- It is either forwarded by SPMD and thus origin endpoint id must be a "normal
world id",
- or initiated by an SP and thus origin endpoint id must be a "secure world id".
Direct messaging
----------------
This is a mandatory interface for Secure Partitions consisting in direct
message request and responses.
The ``ffa_handler`` Hafnium function may:
ID is not consistent:
- trigger a world change e.g. when an SP invokes the direct message
response ABI to a VM.
- handle multiple requests from the NWd without resuming an SP.
- It is either forwarded by SPMD and thus origin endpoint ID must be a "normal
world ID",
- or initiated by an SP and thus origin endpoint ID must be a "secure world ID".
SP-to-SP
~~~~~~~~
- An SP can send a direct message request to another SP
- An SP can receive a direct message response from another SP.
FFA_MSG_SEND_DIRECT_REQ/FFA_MSG_SEND_DIRECT_RESP
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
VM-to-SP
~~~~~~~~
This is a mandatory interface for secure partitions consisting in direct request
and responses with the following rules:
- A VM can send a direct message request to an SP
- An SP can send a direct message response to a VM
- An SP can send a direct request to another SP.
- An SP can receive a direct request from another SP.
- An SP can send a direct response to another SP.
- An SP cannot send a direct request to an Hypervisor or OS kernel.
- An Hypervisor or OS kernel can send a direct request to an SP.
- An SP can send a direct response to an Hypervisor or OS kernel.
SPMC-SPMD messaging
~~~~~~~~~~~~~~~~~~~
SPMC-SPMD direct requests/responses
-----------------------------------
Specific implementation-defined endpoint IDs are allocated to the SPMC and SPMD.
Referring those IDs in source/destination fields of a direct message
request/response permits SPMD to SPMC messaging back and forth.
Implementation-defined FF-A IDs are allocated to the SPMC and SPMD.
Using those IDs in source/destination fields of a direct request/response
permits SPMD to SPMC communication and either way.
Per `[1]`_ Table 114 Config No. 1 (physical FF-A instance):
- SPMC to SPMD direct request/response uses SMC conduit.
- SPMD to SPMC direct request/response uses ERET conduit.
- SPMC=>SPMD direct message request uses SMC conduit
- SPMD=>SPMC direct message request uses ERET conduit
Per `[1]`_ Table 118 Config No. 1 (physical FF-A instance):
- SPMC=>SPMD direct message response uses SMC conduit
- SPMD=>SPMC direct message response uses ERET conduit
Memory management
-----------------
PE MMU configuration
--------------------
This section only deals with the PE MMU configuration.
With secure virtualization enabled, two IPA spaces are output from the secure
EL1&0 Stage-1 translation (secure and non-secure). The EL1&0 Stage-2 translation
hardware is fed by:
Hafnium in the normal world deals with NS buffers only and provisions
a single root page table directory to VMs. In context of S-EL2 enabled
firmware, two IPA spaces are output from Stage-1 translation (secure
and non-secure). The Stage-2 translation handles:
- A single secure IPA space when the SP EL1&0 Stage-1 MMU is disabled.
- Two IPA spaces (secure and non-secure) when the SP EL1&0 Stage-1 MMU is
enabled.
- A single secure IPA space when an SP Stage-1 MMU is disabled.
- Two IPA spaces (secure and non-secure) when Stage-1 MMU is enabled.
``VTCR_EL2`` and ``VSTCR_EL2`` provide configuration bits for controlling the
NS/S IPA translations.
``VSTCR_EL2.SW`` = 0, ``VSTCR_EL2.SA`` = 0,``VTCR_EL2.NSW`` = 0, ``VTCR_EL2.NSA`` = 1:
``VTCR_EL2`` and ``VSTCR_EL2`` provide additional bits for controlling the
NS/S IPA translations (``VSTCR_EL2.SW``, ``VSTCR_EL2.SA``, ``VTCR_EL2.NSW``,
``VTCR_EL2.NSA``). There may be two approaches:
- Stage-2 translations for the NS IPA space access the NS PA space.
- Stage-2 translation table walks for the NS IPA space are to the secure PA space.
- secure and non-secure mappings are rooted as two separate root page
tables
- secure and non-secure mappings use the same root page table. Access
from S-EL1 to an NS region translates to a secure physical address
space access.
Secure and non-secure IPA regions use the same set of Stage-2 page tables within
a SP.
Interrupt management
--------------------
Road to a para-virtualized interface
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GIC ownership
~~~~~~~~~~~~~
Current Hafnium implementation uses an ad-hoc mechanism for a VM to get
a pending interrupt number through an hypercall. The PVM injects
interrupts to VMs by delegation from the Hypervisor. The PVM probes a
pending interrupt directly from the GIC distributor.
The SPMC owns the GIC configuration. Secure and non-secure interrupts are
trapped at S-EL2. The SPMC manages interrupt resources and allocates interrupt
IDs based on SP manifests. The SPMC acknowledges physical interrupts and injects
virtual interrupts by setting the use of vIRQ/vFIQ bits before resuming a SP.
The short-term plan is to have Hafnium/SPMC in the secure world owner
of the GIC configuration.
Non-secure interrupt handling
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The SPMC fully owns the GIC configuration at S-EL2. The SPMC manages
interrupt resources and allocates interrupt ID based on SP manifests.
The SPMC acknowledges physical interrupts and injects virtual interrupts
by setting the vIRQ bit when resuming an SP. A Secure Partition gathers
the interrupt number through an hypercall.
The following illustrate the scenarios of non secure physical interrupts trapped
by the SPMC:
Notice the SPMC/SPMD has to handle Group0 secure interrupts in addition
to Group1 S/NS interrupts.
- The SP handles a managed exit operation:
Power management
----------------
.. image:: ../resources/diagrams/ffa-ns-interrupt-handling-managed-exit.png
Assumption on the Nwd:
- NWd is the best candidate to own the platform Power Management
policy. It is master to invoking PSCI service calls from physical
CPUs.
- EL3 monitor is in charge of the PM control part (its PSCI layer
actually writing to platform registers).
- It is fine for the Hypervisor to trap PSCI calls and relay to EL3, or
OS kernel driver to emit PSCI service calls.
PSCI notification are relayed through the SPMD/SPD PM hooks to the SPMC.
This can either be through re-use of PSCI FIDs or an FF-A direct message
from SPMD to SPMC.
The SPMD performs an exception return to the SPMC which is resumed to
its ``eret_handler`` routine. It is then either consuming a PSCI FID or
an FF-A FID. Depending on the servicing, the SPMC may return directly to
the SPMD (and then NWd) without resuming an SP at this stage. An example
of this is invocation of ``FFA_PARTITION_INFO_GET`` from NWd relayed by
the SPMD to the SPMC. The SPMC returns the needed partition information
to the SPMD (then NWd) without actually resuming a partition in secure world.
*(under discussion)*
About using PSCI FIDs from SPMD to SPMC to notify of PM events, it is still
questioned what to use as the return code from the SPMC.
If the function ID used by the SPMC is not an FF-A ID when doing SMC, then the
EL3 std svc handler won't route the response to the SPMD. That's where comes the
idea to embed the notification into an FF-A message. The SPMC can discriminate
this message as being a PSCI event, process it, and reply with an FF-A return
message that the SPMD receives as an acknowledgement.
SP notification
---------------
- The SP is pre-empted without managed exit:
Power management notifications are conveyed from PSCI library to the
SPMD / SPD hooks. A range of events can be relayed to SPMC.
.. image:: ../resources/diagrams/ffa-ns-interrupt-handling-sp-preemption.png
SPs may need to be notified about specific PM events.
Secure interrupt handling
~~~~~~~~~~~~~~~~~~~~~~~~~
- SPs might register PM events to the SPMC
- On SPMD to SPMC notification, a limited range of SPs may be notified
through a direct message.
- This assumes the mentioned SPs supports managed exit.
The current implementation does not support handling of secure interrupts
trapped by the SPMC at S-EL2. This is work in progress planned for future
releases.
The SPMC is the first to be notified about PM events from the SPMD. It is up
to the SPMC to arbitrate to which SP it needs to send PM events.
An SP explicitly registers to receive notifications to specific PM events.
The register operation can either be an implementation-defined service call
to the SPMC when the primary SP EC boots, or be supplied through the SP
manifest.
Power management
----------------
Support for SMMUv3 in Hafnium
=============================
In platforms with or without secure virtualization:
- The NWd owns the platform PM policy.
- The Hypervisor or OS kernel is the component initiating PSCI service calls.
- The EL3 PSCI library is in charge of the PM coordination and control
(eventually writing to platform registers).
- While coordinating PM events, the PSCI library calls backs into the Secure
Payload Dispatcher for events the latter has statically registered to.
When using the SPMD as a Secure Payload Dispatcher:
- A power management event is relayed through the SPD hook to the SPMC.
- In the current implementation only cpu on (svc_on_finish) and cpu off
(svc_off) hooks are registered.
- The behavior for the cpu on event is described in `Secondary cores boot-up`_.
The SPMC is entered through its secondary physical core entry point.
- The cpu off event occurs when the NWd calls PSCI_CPU_OFF. The method by which
the PM event is conveyed to the SPMC is implementation-defined in context of
FF-A v1.0 (`SPMC-SPMD direct requests/responses`_). It consists in a SPMD-to-SPMC
direct request/response conveying the PM event details and SPMC response.
The SPMD performs a synchronous entry into the SPMC. The SPMC is entered and
updates its internal state to reflect the physical core is being turned off.
In the current implementation no SP is resumed as a consequence. This behavior
ensures a minimal support for CPU hotplug e.g. when initiated by the NWd linux
userspace.
SMMUv3 support in Hafnium
=========================
An SMMU is analogous to an MMU in a CPU. It performs address translations for
Direct Memory Access (DMA) requests from system I/O devices.
......@@ -856,7 +829,7 @@ several I/O devices along with Interconnect and Memory system.
.. image:: ../resources/diagrams/MMU-600.png
SMMU has several versions including SMMUv1, SMMUv2 and SMMUv3. Hafnium provides
support for SMMUv3 driver in both Normal and Secure World. A brief introduction
support for SMMUv3 driver in both normal and secure world. A brief introduction
of SMMUv3 functionality and the corresponding software support in Hafnium is
provided here.
......@@ -956,7 +929,7 @@ References
.. _[3]:
[3] `Trusted Boot Board Requirements
Client <https://developer.arm.com/docs/den0006/latest/trusted-board-boot-requirements-client-tbbr-client-armv8-a>`__
Client <https://developer.arm.com/documentation/den0006/d/>`__
.. _[4]:
......@@ -964,7 +937,7 @@ Client <https://developer.arm.com/docs/den0006/latest/trusted-board-boot-require
.. _[5]:
[5] https://git.trustedfirmware.org/TF-A/tf-a-tests.git/tree/spm/cactus/cactus.dts
[5] https://git.trustedfirmware.org/TF-A/tf-a-tests.git/tree/spm/cactus/plat/arm/fvp/fdts/cactus.dts
.. _[6]:
......@@ -976,7 +949,7 @@ Client <https://developer.arm.com/docs/den0006/latest/trusted-board-boot-require
.. _[8]:
[8] https://developer.trustedfirmware.org/w/tf_a/poc-multiple-signing-domains/
[8] https://lists.trustedfirmware.org/pipermail/tf-a/2020-February/000296.html
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