[PATCH] arm64: mm: When logging data aborts only decode Xs when ISV=1

[PATCH] arm64: mm: When logging data aborts only decode Xs when ISV=1

[Mark Brown]

When logging the decode of a data abort we currently unconditionally decode
and display Xs. Currently the only defined non-RES0 values for this field
are for cases where ISV=1, move the decode of Xs into our existing check
for ISV=1. This avoids potential confusion if some other use is assigned to
these bits for ISV=0 cases in future, or misleading someone into thinking
there is a meaningful value there with currently defined architecture.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 arch/arm64/mm/fault.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 85e23388f9bb..0b52557652be 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -76,6 +76,8 @@ static void data_abort_decode(unsigned long esr)
 		pr_alert("  SF = %lu, AR = %lu\n",
 			 (esr & ESR_ELx_SF) >> ESR_ELx_SF_SHIFT,
 			 (esr & ESR_ELx_AR) >> ESR_ELx_AR_SHIFT);
+		pr_alert("  Xs = %llu\n",
+			 (iss2 & ESR_ELx_Xs_MASK) >> ESR_ELx_Xs_SHIFT);
 	} else {
 		pr_alert("  ISV = 0, ISS = 0x%08lx, ISS2 = 0x%08lx\n",
 			 esr & ESR_ELx_ISS_MASK, iss2);
@@ -87,11 +89,10 @@ static void data_abort_decode(unsigned long esr)
 		 (iss2 & ESR_ELx_TnD) >> ESR_ELx_TnD_SHIFT,
 		 (iss2 & ESR_ELx_TagAccess) >> ESR_ELx_TagAccess_SHIFT);
 
-	pr_alert("  GCS = %ld, Overlay = %lu, DirtyBit = %lu, Xs = %llu\n",
+	pr_alert("  GCS = %ld, Overlay = %lu, DirtyBit = %lu\n",
 		 (iss2 & ESR_ELx_GCS) >> ESR_ELx_GCS_SHIFT,
 		 (iss2 & ESR_ELx_Overlay) >> ESR_ELx_Overlay_SHIFT,
-		 (iss2 & ESR_ELx_DirtyBit) >> ESR_ELx_DirtyBit_SHIFT,
-		 (iss2 & ESR_ELx_Xs_MASK) >> ESR_ELx_Xs_SHIFT);
+		 (iss2 & ESR_ELx_DirtyBit) >> ESR_ELx_DirtyBit_SHIFT);
 }
 
 static void mem_abort_decode(unsigned long esr)

---
base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482
change-id: 20260618-arm64-xs-decode-aa1316410455

Best regards,
--  
Mark Brown <broonie@kernel.org>

Re: [PATCH] arm64: mm: When logging data aborts only decode Xs when ISV=1

[Will Deacon]

On Thu, 02 Jul 2026 20:13:35 +0100, Mark Brown wrote:
> When logging the decode of a data abort we currently unconditionally decode
> and display Xs. Currently the only defined non-RES0 values for this field
> are for cases where ISV=1, move the decode of Xs into our existing check
> for ISV=1. This avoids potential confusion if some other use is assigned to
> these bits for ISV=0 cases in future, or misleading someone into thinking
> there is a meaningful value there with currently defined architecture.
> 
> [...]

Applied to arm64 (for-next/fixes), thanks!

[1/1] arm64: mm: When logging data aborts only decode Xs when ISV=1
      https://git.kernel.org/arm64/c/f797f51a185f

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev