[PATCH] arm64: errata: match the target implementation CPU's own MIDR
From: David Carlier <hidden>
Date: 2026-09-06 12:14:26
Also in:
lkml, stable
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
__is_affected_midr_range() is handed the MIDR and REVIDR of one target
implementation CPU, but tests the erratum's range with is_midr_in_range(),
which re-scans all of target_impl_cpus[] and ignores the @midr argument.
The range test is thus constant across the per-CPU loop in
is_affected_midr_range() and only answers "is any target CPU in range".
Since just the fixed_revs REVIDR check uses the iteration's own registers,
an out-of-range target CPU can decide whether a MIDR_FIXED() exemption
applies. A VM then enables a workaround whose only in-range CPU is fixed
silicon, e.g. erratum 2658417 on a Cortex-A510 r1p1 with REVIDR_EL1[25]
set.
Factor the range test into __is_midr_in_range(), which takes an explicit
MIDR, and use it in __is_affected_midr_range().
Fixes: 86edf6bdcf05 ("smccc/kvm_guest: Enable errata based on implementation CPUs")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-5
Signed-off-by: David Carlier <redacted>
---
arch/arm64/kernel/cpu_errata.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index b33dccfafaf8..8ec47d89b45b 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c@@ -28,18 +28,21 @@ bool cpu_errata_set_target_impl(u64 num, void *impl_cpus) return true; } +static inline bool __is_midr_in_range(u32 midr, struct midr_range const *range) +{ + return midr_is_cpu_model_range(midr, range->model, + range->rv_min, range->rv_max); +} + static inline bool is_midr_in_range(struct midr_range const *range) { int i; if (!target_impl_cpu_num) - return midr_is_cpu_model_range(read_cpuid_id(), range->model, - range->rv_min, range->rv_max); + return __is_midr_in_range(read_cpuid_id(), range); for (i = 0; i < target_impl_cpu_num; i++) { - if (midr_is_cpu_model_range(target_impl_cpus[i].midr, - range->model, - range->rv_min, range->rv_max)) + if (__is_midr_in_range(target_impl_cpus[i].midr, range)) return true; } return false;
@@ -59,7 +62,7 @@ __is_affected_midr_range(const struct arm64_cpu_capabilities *entry, u32 midr, u32 revidr) { const struct arm64_midr_revidr *fix; - if (!is_midr_in_range(&entry->midr_range)) + if (!__is_midr_in_range(midr, &entry->midr_range)) return false; midr &= MIDR_REVISION_MASK | MIDR_VARIANT_MASK;
--
2.55.0