KVM: SVM: fix guest global tlb flushes with NPT

(cherry picked from commit e5eab0ce)

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

arch/x86/kvm/svm.c

@@ -880,6 +880,10 @@ 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)