KVM: vmx: obey KVM_QUIRK_CD_NW_CLEARED

OVMF depends on WB to boot fast, because it only clears caches after
it has set up MTRRs---which is too late.

Let's do writeback if CR0.CD is set to make it happy, similar to what
SVM is already doing.

Signed-off-by: Xiao Guangrong <[e-mail]>
Tested-by: Alex Williamson <[e-mail]>
Signed-off-by: Paolo Bonzini <[e-mail]>

arch/x86/kvm/vmx.c

···
 
 	if (kvm_read_cr0(vcpu) & X86_CR0_CD) {
 		ipat = VMX_EPT_IPAT_BIT;
-		cache = MTRR_TYPE_UNCACHABLE;
+		if (kvm_check_has_quirk(vcpu->kvm, KVM_QUIRK_CD_NW_CLEARED))
+			cache = MTRR_TYPE_WRBACK;
+		else
+			cache = MTRR_TYPE_UNCACHABLE;
 		goto exit;
 	}