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KVM: x86: NOP emulation clears (incorrectly) the high 32-bits of RAX

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On long-mode the current NOP (0x90) emulation still writes back to RAX.  As a
result, EAX is zero-extended and the high 32-bits of RAX are cleared.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Nadav Amit 2014-06-15 16:13:01 +03:00 committed by Paolo Bonzini
parent 140bad89fd
commit a825f5cc4a
1 changed files with 3 additions and 2 deletions
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5
arch/x86/kvm/emulate.c
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@ -4688,8 +4688,9 @@ special_insn:
break;
case 0x90 ... 0x97: /* nop / xchg reg, rax */
if (ctxt->dst.addr.reg == reg_rmw(ctxt, VCPU_REGS_RAX))
break;
rc = em_xchg(ctxt);
ctxt->dst.type = OP_NONE;
else
rc = em_xchg(ctxt);
break;
case 0x98: /* cbw/cwde/cdqe */
switch (ctxt->op_bytes) {