Re: [PATCH] KVM: x86 emulator: cleanup for BitOp instruction emulation

[Paolo Bonzini <pbonzini@redhat.com>]

On 08/04/2010 11:01 AM, Wei Yongjun wrote:
> Signed-off-by: Wei Yongjun<yjwei@cn.fujitsu.com>
> ---
>   arch/x86/kvm/emulate.c |   12 ++++--------
>   1 files changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index eba5a67..c05a5d7 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -2545,6 +2545,10 @@ done_prefixes:
>   		break;
>   	}
> 
> +	/* Only subword offset for BitOp: bt/bts/btr/btc. */
> +	if (c->d&  BitOp)
> +		c->src.val&= (c->op_bytes<<  3) - 1;
> +

You are doing this before the destination operand is decoded, which
means you are not adjusting a memory operand anymore if c->src.val >
(c->op_bytes * 8).

Paolo