Merge pull request #1887 from ambroise-arm/av/a76-cve

Cortex-A76: Optimize CVE_2018_3639 workaround

lib/cpus/aarch64/cortex_a76.S

@@ -13,20 +13,17 @@
 #include <plat_macros.S>
 #include <services/arm_arch_svc.h>
 
-#if !DYNAMIC_WORKAROUND_CVE_2018_3639
-#error Cortex A76 requires DYNAMIC_WORKAROUND_CVE_2018_3639=1
-#endif
-
 #define ESR_EL3_A64_SMC0	0x5e000000
 #define ESR_EL3_A32_SMC0	0x4e000000
 
+#if DYNAMIC_WORKAROUND_CVE_2018_3639
 	/*
 	 * This macro applies the mitigation for CVE-2018-3639.
-	 * It implements a fash path where `SMCCC_ARCH_WORKAROUND_2`
+	 * It implements a fast path where `SMCCC_ARCH_WORKAROUND_2`
 	 * SMC calls from a lower EL running in AArch32 or AArch64
 	 * will go through the fast and return early.
 	 *
-	 * The macro saves x2-x3 to the context.  In the fast path
+	 * The macro saves x2-x3 to the context. In the fast path
 	 * x0-x3 registers do not need to be restored as the calling
 	 * context will have saved them.
 	 */
@@ -63,7 +60,7 @@
 		 * When the calling context wants mitigation disabled,
 		 * we program the mitigation disable function in the
 		 * CPU context, which gets invoked on subsequent exits from
-		 * EL3 via the `el3_exit` function.  Otherwise NULL is
+		 * EL3 via the `el3_exit` function. Otherwise NULL is
 		 * programmed in the CPU context, which results in caller's
 		 * inheriting the EL3 mitigation state (enabled) on subsequent
 		 * `el3_exit`.
@@ -82,7 +79,7 @@
 	.endif
 1:
 	/*
-	 * Always enable v4 mitigation during EL3 execution.  This is not
+	 * Always enable v4 mitigation during EL3 execution. This is not
 	 * required for the fast path above because it does not perform any
 	 * memory loads.
 	 */
@@ -188,6 +185,7 @@ vector_entry cortex_a76_serror_aarch32
 	apply_cve_2018_3639_wa _is_sync_exception=0 _esr_el3_val=ESR_EL3_A32_SMC0
 	b	serror_aarch32
 end_vector_entry cortex_a76_serror_aarch32
+#endif /* DYNAMIC_WORKAROUND_CVE_2018_3639 */
 
 	/* --------------------------------------------------
 	 * Errata Workaround for Cortex A76 Errata #1073348.
@@ -319,9 +317,13 @@ func cortex_a76_reset_func
 	/* If the PE implements SSBS, we don't need the dynamic workaround */
 	mrs	x0, id_aa64pfr1_el1
 	lsr	x0, x0, #ID_AA64PFR1_EL1_SSBS_SHIFT
-	and     x0, x0, #ID_AA64PFR1_EL1_SSBS_MASK
+	and	x0, x0, #ID_AA64PFR1_EL1_SSBS_MASK
+#if !DYNAMIC_WORKAROUND_CVE_2018_3639 && ENABLE_ASSERTIONS
+	cmp	x0, 0
+	ASM_ASSERT(ne)
+#endif
+#if DYNAMIC_WORKAROUND_CVE_2018_3639
 	cbnz	x0, 1f
-
 	mrs	x0, CORTEX_A76_CPUACTLR2_EL1
 	orr	x0, x0, #CORTEX_A76_CPUACTLR2_EL1_DISABLE_LOAD_PASS_STORE
 	msr	CORTEX_A76_CPUACTLR2_EL1, x0
@@ -330,16 +332,17 @@ func cortex_a76_reset_func
 #ifdef IMAGE_BL31
 	/*
 	 * The Cortex-A76 generic vectors are overwritten to use the vectors
-	 * defined above.  This is required in order to apply mitigation
+	 * defined above. This is required in order to apply mitigation
 	 * against CVE-2018-3639 on exception entry from lower ELs.
 	 */
 	adr	x0, cortex_a76_wa_cve_2018_3639_a76_vbar
 	msr	vbar_el3, x0
 	isb
-#endif
+#endif /* IMAGE_BL31 */
 
 1:
-#endif
+#endif /* DYNAMIC_WORKAROUND_CVE_2018_3639 */
+#endif /* WORKAROUND_CVE_2018_3639 */
 
 #if ERRATA_DSU_936184
 	bl	errata_dsu_936184_wa