KVM: x86/mmu: Zap SPTEs when CR0.CD is toggled iff guest MTRRs are honored

Zap SPTEs when CR0.CD is toggled if and only if KVM's MMU is honoring
guest MTRRs, which is the only time that KVM incorporates the guest's
CR0.CD into the final memtype.

Suggested-by: Chao Gao <[email protected]>
Signed-off-by: Yan Zhao <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[sean: rephrase shortlog]
Signed-off-by: Sean Christopherson <[email protected]>

Author: yanzhao56

arch/x86/kvm/x86.c

@@ -962,7 +962,7 @@ void kvm_post_set_cr0(struct kvm_vcpu *vcpu, unsigned long old_cr0, unsigned lon
 		kvm_mmu_reset_context(vcpu);
 
 	if (((cr0 ^ old_cr0) & X86_CR0_CD) &&
-	    kvm_arch_has_noncoherent_dma(vcpu->kvm) &&
+	    kvm_mmu_honors_guest_mtrrs(vcpu->kvm) &&
 	    !kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_CD_NW_CLEARED))
 		kvm_zap_gfn_range(vcpu->kvm, 0, ~0ULL);
 }