KVM: Load real mode segments correctly

Real mode segments to not reference the GDT or LDT; they simply compute
base = selector * 16.

Signed-off-by: Avi Kivity <avi@qumranet.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 22edd95..bfc7c33 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3588,11 +3588,33 @@ static int load_segment_descriptor_to_kvm_desct(struct kvm_vcpu *vcpu,
        return 0;
 }
 
+int kvm_load_realmode_segment(struct kvm_vcpu *vcpu, u16 selector, int seg)
+{
+       struct kvm_segment segvar = {
+               .base = selector << 4,
+               .limit = 0xffff,
+               .selector = selector,
+               .type = 3,
+               .present = 1,
+               .dpl = 3,
+               .db = 0,
+               .s = 1,
+               .l = 0,
+               .g = 0,
+               .avl = 0,
+               .unusable = 0,
+       };
+       kvm_x86_ops->set_segment(vcpu, &segvar, seg);
+       return 0;
+}
+
 int kvm_load_segment_descriptor(struct kvm_vcpu *vcpu, u16 selector,
                                int type_bits, int seg)
 {
        struct kvm_segment kvm_seg;
 
+       if (!(vcpu->arch.cr0 & X86_CR0_PE))
+               return kvm_load_realmode_segment(vcpu, selector, seg);
        if (load_segment_descriptor_to_kvm_desct(vcpu, selector, &kvm_seg))
                return 1;
        kvm_seg.type |= type_bits;