Messages in this thread Patch in this message | | | From | Nadav Amit <> | Subject | [PATCH v2 5/9] KVM: x86: NOP emulation clears (incorrectly) the high 32-bits of RAX | Date | Wed, 18 Jun 2014 17:19:22 +0300 |
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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> --- arch/x86/kvm/emulate.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index b354531..eb93eb4 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -4663,8 +4663,9 @@ 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) { -- 1.9.1
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