KVM: SVM: fix guest global tlb flushes with NPT

Accesses to CR4 are intercepted even with Nested Paging enabled. But the code
does not check if the guest wants to do a global TLB flush. So this flush gets
lost. This patch adds the check and the flush to svm_set_cr4.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

arch/x86/kvm/svm.c

@@ -879,6 +879,10 @@ set:
 static void svm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
 {
 	unsigned long host_cr4_mce = read_cr4() & X86_CR4_MCE;
+	unsigned long old_cr4 = to_svm(vcpu)->vmcb->save.cr4;
+
+	if (npt_enabled && ((old_cr4 ^ cr4) & X86_CR4_PGE))
+		force_new_asid(vcpu);
 
 	vcpu->arch.cr4 = cr4;
 	if (!npt_enabled)