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>

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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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arch/arm64/kernel/cpu_errata.c

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