KVM: x86 emulator: Leave segment limit and attributs alone in real mode

When loading a segment in real mode, only the base and selector must
be modified.  The limit needs to be left alone, otherwise big real mode
users will hit a #GP due to limit checking (currently this is suppressed
because we don't check limits in real mode).

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

1 files changed, 2 insertions, 6 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 5e27ba532613..f8b27cd2a6cb 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1388,19 +1388,15 @@ static int load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
         bool null_selector = !(selector & ~0x3); /* 0000-0003 are null */
         ulong desc_addr;
         int ret;
+        u16 dummy;
 
         memset(&seg_desc, 0, sizeof seg_desc);
 
         if ((seg <= VCPU_SREG_GS && ctxt->mode == X86EMUL_MODE_VM86)
             || ctxt->mode == X86EMUL_MODE_REAL) {
                 /* set real mode segment descriptor */
+                ctxt->ops->get_segment(ctxt, &dummy, &seg_desc, NULL, seg);
                 set_desc_base(&seg_desc, selector << 4);
-                set_desc_limit(&seg_desc, 0xffff);
-                seg_desc.type = 3;
-                seg_desc.p = 1;
-                seg_desc.s = 1;
-                if (ctxt->mode == X86EMUL_MODE_VM86)
-                        seg_desc.dpl = 3;
                 goto load;
         }