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KVM: x86: Prioritize CPUID faulting over CPUID VM-exits in nested VMX

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Per the Intel SDM, "Certain exceptions have priority over VM exits.  These
include invalid-opcode exceptions, faults based on privilege level, and
general-protection exceptions that are based on checking I/O permission
bits in the task-state segment (TSS)."

Ensure that when L2 executes CPUID at CPL > 0 while L1 has enabled CPUID
faulting, KVM intercepts the exit in L0 and queues #GP rather than
forwarding the CPUID VM-exit to L1.

Empirical testing confirms that this #GP has higher precedence than a CPUID
VM-exit on Granite Rapids (F/M/S 6/0xad/1).

Fixes: db2336a804 ("KVM: x86: virtualize cpuid faulting")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/patchset/20260513224608.1859737-1-jmattson%40google.com?part=3
Signed-off-by: Jim Mattson <jmattson@google.com>
Link: https://patch.msgid.link/20260527174347.2356165-3-jmattson@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Jim Mattson 2026-05-27 10:43:44 -07:00 committed by Sean Christopherson
parent cf7d65d1d6
commit be7fd7c3e8
1 changed files with 2 additions and 0 deletions
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2
arch/x86/kvm/vmx/nested.c
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@ -6552,6 +6552,8 @@ static bool nested_vmx_l0_wants_exit(struct kvm_vcpu *vcpu,
nested_evmcs_l2_tlb_flush_enabled(vcpu) &&
kvm_hv_is_tlb_flush_hcall(vcpu);
#endif
case EXIT_REASON_CPUID:
return !kvm_is_cpuid_allowed(vcpu);
default:
break;
}