WARN and continue if a write to the PAT MSR reaches kvm_set_msr_common() now that both VMX and SVM handle PAT writes entirely on their own. Keep the case statement with a WARN instead of dropping it entirely to document why KVM's handling of reads and writes isn't symmetrical (reads are still handled by kvm_get_msr_common(). Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> --- arch/x86/kvm/x86.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 8b356c9d8a81..c36256d00250 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3701,6 +3701,12 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) } break; case MSR_IA32_CR_PAT: + /* + * Writes to PAT should be handled by vendor code as both SVM + * and VMX track the guest's PAT in the VMCB/VMCS. + */ + WARN_ON_ONCE(1); + fallthrough; case MTRRphysBase_MSR(0) ... MSR_MTRRfix4K_F8000: case MSR_MTRRdefType: return kvm_mtrr_set_msr(vcpu, msr, data); -- 2.40.1.495.gc816e09b53d-goog
