KVM: fix sil/dil/bpl/spl in the mod/rm fields

The x86-64 extended low-byte registers were fetched correctly from reg,
but not from mod/rm.

This fixes another bug in the boot of RHEL5.9 64-bit, but it is still
not enough.

Cc: <stable@vger.kernel.org> # 3.9
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 0f42c2a48166..5953dcea752d 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1240,9 +1240,12 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt,
         ctxt->modrm_seg = VCPU_SREG_DS;
 
         if (ctxt->modrm_mod == 3) {
+                int highbyte_regs = ctxt->rex_prefix == 0;
+
                 op->type = OP_REG;
                 op->bytes = (ctxt->d & ByteOp) ? 1 : ctxt->op_bytes;
-                op->addr.reg = decode_register(ctxt, ctxt->modrm_rm, ctxt->d & ByteOp);
+                op->addr.reg = decode_register(ctxt, ctxt->modrm_rm,
+                                               highbyte_regs && (ctxt->d & ByteOp));
                 if (ctxt->d & Sse) {
                         op->type = OP_XMM;
                         op->bytes = 16;