arm64: cpufeature: Make PMUVer and PerfMon unsigned

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On the host, this change doesn't make a difference because the fields
are defined as FTR_EXACT. However, KVM allows userspace to set these
fields for a guest and overrides the type to be FTR_LOWER_SAFE. And
while KVM used to do an unsigned comparison to validate that the new
value is lower than what the hardware provides, since the linked commit
it uses the generic sanitization framework which does a signed
comparison.

Fix it by defining these fields as unsigned. In theory, without this
fix, userspace could set a higher PMU version than the hardware supports
by providing any value with the top bit set.

Fixes: c118cead07 ("KVM: arm64: Use generic sanitisation for ID_(AA64)DFR0_EL1")
Signed-off-by: James Clark <james.clark@linaro.org>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Colton Lewis <coltonlewis@google.com>
Signed-off-by: Will Deacon <will@kernel.org>

...

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James Clark 2026-03-05 16:28:18 +00:00 • committed by Will Deacon

parent 2e30447b23

commit d1dcc20bcc

1 changed files with 2 additions and 2 deletions

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arch/arm64/kernel/cpufeature.c

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