KVM relies on ARM64_WORKAROUND_PMUV3_IMPDEF_TRAPS as a system-wide
precondition for PMUv3 emulation on affected Apple CPUs. A local CPU
erratum is too weak for that: once the workaround is enabled, a late CPU
that misses it may still be onlined.
Make the workaround an all-early-CPU capability instead. The matcher is
still local because it depends on MIDR_EL1, but the capability is only
advertised if all early CPUs match. A late CPU that misses an advertised
capability is therefore rejected.
Although kept in the errata capability table, this capability describes
optional trap support rather than a workaround required for safe CPU
operation. A late CPU may therefore match it when the system does not.
KVM treats an IMPDEF PMU as unimplemented unless the capability was
finalized system-wide, so the additional trap support remains unused.
Fixes: bed9b8ec8c71 ("KVM: arm64: Advertise PMUv3 if IMPDEF traps are present")
Assisted-by: Codex:gpt-5.5
Signed-off-by: Akihiko Odaki <[email protected]>
---
arch/arm64/kernel/cpu_errata.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 1995e1198648..a5ae628204a1 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -1005,7 +1005,7 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
{
.desc = "Apple IMPDEF PMUv3 Traps",
.capability = ARM64_WORKAROUND_PMUV3_IMPDEF_TRAPS,
- .type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,
+ .type = ARM64_CPUCAP_EARLY_LOCAL_CPU_FEATURE,
.matches = has_impdef_pmuv3,
.cpu_enable = cpu_enable_impdef_pmuv3_traps,
},
--
2.55.0
