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

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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>
This commit is contained in:
Avi Kivity 2012-08-21 17:07:04 +03:00 committed by Marcelo Tosatti
parent e2a610d7fc
commit 03ebebeb1f
1 changed files with 2 additions and 6 deletions
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8
arch/x86/kvm/emulate.c
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@ -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;
}