arm64: KVM: Add workaround for Cortex-A57 erratum 834220

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.

Cc: stable@vger.kernel.org
Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 9ac16a4..e55848c 100644 (file)
--- 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 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 11d5bb0..52722ee 100644 (file)
--- 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 (file)
--- 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 (file)
--- 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