KVM: VMX: Allow real mode emulation using vm86 with dpl=0

Real mode is always entered from protected mode with dpl=0.  Since
the dpl doesn't affect execution, and we already override it to 3
in the vmcs (as vmx requires), we can allow execution in that state.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 88eeb405560f406f48b1f143939aaa0a9fe9ca05..4811d91759a11d123e30053415c49595b6cdc4f7 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3317,7 +3317,7 @@ static bool rmode_segment_valid(struct kvm_vcpu *vcpu, int seg)
                return false;
        if (var.limit != 0xffff)
                return false;
-       if (ar != 0xf3)
+       if ((ar | (3 << AR_DPL_SHIFT)) != 0xf3)
                return false;
 
        return true;