[Devel] [PATCH hci-8.1 v2 4/5] x86/traps: decode the faulting CPUID with the instruction decoder

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> check_cpuid_fault() reads two bytes at the faulting ip and emulates
> only when they are 0f a2, the bare CPUID encoding.
> 
> CPUID has no operands, so the CPU accepts and ignores every legacy
> and REX prefix in front of it. All of these are valid CPUID and raise
> the same #GP(0) when CPUID faulting is on:
> 
>   0f a2           cpuid
>   66 0f a2        data16 cpuid       (operand-size override)
>   f3 0f a2        repz cpuid
>   2e 0f a2        cs cpuid           (segment override)
>   48 0f a2        rex.W cpuid
> 
> Only the first one is recognised. For the others the handler reads
> the prefix byte instead of the opcode, declines, and the task is
> [ ... ]
> Fixes: 1033fe455434 ("arch/x86: introduce cpuid override")
> https://virtuozzo.atlassian.net/browse/VSTOR-148843
> 
> Feature: x86: cpu pools (cpuid override)
> Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.vzint.dev/#/patchset/20261006-b4-prep-khorenko-vstor-148656-cpuid-v2-0-f6d1192c7d60@virtuozzo.com?part=4