From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
Explicit segment overides other than %fs and %gs are documented as ignored by
both Intel and AMD.
In practice, this means that:
* Explicit uses of %ss don't actually yield #SS[0] for non-canonical
memory references.
* Explicit uses of %{e,c,d}s don't override %rbp/%rsp-based memory references
to yield #GP[0] for non-canonical memory references.
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
---
arch/x86/kvm/emulate.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index dd88158..5091255 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -5148,8 +5148,10 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
case 0x2e: /* CS override */
case 0x36: /* SS override */
case 0x3e: /* DS override */
- has_seg_override = true;
- ctxt->seg_override = (ctxt->b >> 3) & 3;
+ if (mode != X86EMUL_MODE_PROT64) {
+ has_seg_override = true;
+ ctxt->seg_override = (ctxt->b >> 3) & 3;
+ }
break;
case 0x64: /* FS override */
case 0x65: /* GS override */
--
2.7.4
