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>

1 files changed, 6 insertions, 0 deletions

diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
index 1599701ef044..ff2e038f0007 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