Cortex-A57 parts up to r1p2 can misreport Stage 2 translation faults
when a Stage 1 permission fault or device alignment fault should
have been reported.
This patch implements the workaround (which is to validate that the
Stage-1 translation actually succeeds) by using code patching.
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
---
arch/arm64/Kconfig | 21 +++++++++++++++++++++
arch/arm64/include/asm/cpufeature.h | 3 ++-
arch/arm64/kernel/cpu_errata.c | 9 +++++++++
arch/arm64/kvm/hyp.S | 6 ++++++
4 files changed, 38 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 9ac16a4..746d985 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -316,6 +316,27 @@ config ARM64_ERRATUM_832075
If unsure, say Y.
+config ARM64_ERRATUM_834220
+ bool "Cortex-A57: 834220: Stage 2 translation fault might be incorrectly reported in presence of a Stage 1 fault"
+ depends on KVM
+ default y
+ help
+ This option adds an alternative code sequence to work around ARM
+ erratum 834220 on Cortex-A57 parts up to r1p2.
+
+ Affected Cortex-A57 parts might report a Stage 2 translation
+ fault as a the result of a Stage 1 fault for load crossing a
+ page boundary when there is a permission or device memory
+ alignment fault at Stage 1 and a translation fault at Stage 2.
+
+ The workaround is to verify that the Stage-1 translation
+ doesn't generate a fault before handling the Stage-2 fault.
+ Please note that this does not necessarily enable the workaround,
+ as it depends on the alternative framework, which will only patch
+ the kernel if an affected CPU is detected.
+
+ If unsure, say Y.
+
config ARM64_ERRATUM_845719
bool "Cortex-A53: 845719: a load might read incorrect data"
depends on COMPAT
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 11d5bb0f..52722ee 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -29,8 +29,9 @@
#define ARM64_HAS_PAN 4
#define ARM64_HAS_LSE_ATOMICS 5
#define ARM64_WORKAROUND_CAVIUM_23154 6
+#define ARM64_WORKAROUND_834220 7
-#define ARM64_NCAPS 7
+#define ARM64_NCAPS 8
#ifndef __ASSEMBLY__
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 24926f2..feb6b4e 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -75,6 +75,15 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
(1 << MIDR_VARIANT_SHIFT) | 2),
},
#endif
+#ifdef CONFIG_ARM64_ERRATUM_834220
+ {
+ /* Cortex-A57 r0p0 - r1p2 */
+ .desc = "ARM erratum 834220",
+ .capability = ARM64_WORKAROUND_834220,
+ MIDR_RANGE(MIDR_CORTEX_A57, 0x00,
+ (1 << MIDR_VARIANT_SHIFT) | 2),
+ },
+#endif
#ifdef CONFIG_ARM64_ERRATUM_845719
{
/* Cortex-A53 r0p[01234] */
diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
index 1599701..ff2e038 100644
--- a/arch/arm64/kvm/hyp.S
+++ b/arch/arm64/kvm/hyp.S
@@ -1015,9 +1015,15 @@ el1_trap:
b.ne 1f // Not an abort we care about
/* This is an abort. Check for permission fault */
+alternative_if_not ARM64_WORKAROUND_834220
and x2, x1, #ESR_ELx_FSC_TYPE
cmp x2, #FSC_PERM
b.ne 1f // Not a permission fault
+alternative_else
+ nop // Use the permission fault path to
+ nop // check for a valid S1 translation,
+ nop // regardless of the ESR value.
+alternative_endif
/*
* Check for Stage-1 page table walk, which is guaranteed
--
2.1.4
--
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