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arm64: errata: match the target implementation CPU's own MIDR

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__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: 86edf6bdcf ("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 <devnexen@gmail.com>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
David Carlier 2026-09-06 13:14:16 +01:00 committed by Will Deacon
parent baaa9b126b
commit b7403afb7a
1 changed files with 9 additions and 6 deletions
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15
arch/arm64/kernel/cpu_errata.c
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@ -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;