KVM: x86: Apply runtime updates to current CPUID during KVM_SET_CPUID{,2}

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commit e2b43fb252 upstream.

When handling KVM_SET_CPUID{,2}, do runtime CPUID updates on the vCPU's
current CPUID (and caps) prior to swapping in the incoming CPUID state so
that KVM doesn't lose pending updates if the incoming CPUID is rejected,
and to prevent a false failure on the equality check.

Note, runtime updates are unconditionally performed on the incoming/new
CPUID (and associated caps), i.e. clearing the dirty flag won't negatively
affect the new CPUID.

Fixes: 93da6af3ae ("KVM: x86: Defer runtime updates of dynamic CPUID bits until CPUID emulation")
Reported-by: Igor Mammedov <imammedo@redhat.com>
Closes: https://lore.kernel.org/all/20251128123202.68424a95@imammedo
Cc: stable@vger.kernel.org
Acked-by: Igor Mammedov <imammedo@redhat.com>
Tested-by: Igor Mammedov <imammedo@redhat.com>
Link: https://patch.msgid.link/20251202015049.1167490-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

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Sean Christopherson 2025-12-01 17:50:48 -08:00 • committed by Greg Kroah-Hartman

parent aedf238216

commit caf68b6da3

1 changed files with 9 additions and 2 deletions

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arch/x86/kvm/cpuid.c

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