From a825f5cc4a8455663562809748240169cb9bc2c0 Mon Sep 17 00:00:00 2001 From: Nadav Amit Date: Sun, 15 Jun 2014 16:13:01 +0300 Subject: [PATCH] KVM: x86: NOP emulation clears (incorrectly) the high 32-bits of RAX 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 Signed-off-by: Paolo Bonzini --- 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 6f09b2e555ef..84dc4ba0364d 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -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) {