KVM: SVM: Sync efer back into nested vmcb

This patch fixes a bug in a nested hypervisor that heavily
switches between real-mode and long-mode. The problem is
fixed by syncing back efer into the guest vmcb on emulated
vmexit.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 8a3f9f64f86f..09704a0501d7 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1896,6 +1896,7 @@ static int nested_svm_vmexit(struct vcpu_svm *svm)
         nested_vmcb->save.ds     = vmcb->save.ds;
         nested_vmcb->save.gdtr   = vmcb->save.gdtr;
         nested_vmcb->save.idtr   = vmcb->save.idtr;
+        nested_vmcb->save.efer   = svm->vcpu.arch.efer;
         nested_vmcb->save.cr0    = kvm_read_cr0(&svm->vcpu);
         nested_vmcb->save.cr3    = svm->vcpu.arch.cr3;
         nested_vmcb->save.cr2    = vmcb->save.cr2;