From: Avi Kivity <avi@redhat.com>
To: Wei Yongjun <yjwei@cn.fujitsu.com>
Cc: kvm@vger.kernel.org
Subject: Re: [PATCH] KVM: x86 emulator: add bsf/bsr instruction emulation
Date: Mon, 09 Aug 2010 23:14:21 -0400 [thread overview]
Message-ID: <4C60C40D.7070905@redhat.com> (raw)
In-Reply-To: <4C5FD1A5.5040805@cn.fujitsu.com>
On 08/09/2010 06:00 AM, Wei Yongjun wrote:
> Add bsf/bsr instruction emulation (opcode 0x0f 0xbc~0xbd)
>
> @@ -3464,6 +3464,30 @@ twobyte_insn:
> btc: /* btc */
> emulate_2op_SrcV_nobyte("btc", c->src, c->dst, ctxt->eflags);
> break;
> + case 0xbc: { /* bsf */
> + int zf;
> + __asm__ ("bsf %2, %0; setz %b1"
> + : "=r"(c->dst.val), "=q"(zf)
> + : "r"(c->src.val), "1" (0));
Won't the high bytes of zf remain clear? Please examine the assembly.
Declaring it u8 is probably better.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
next prev parent reply other threads:[~2010-08-10 3:14 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-09 10:00 [PATCH] KVM: x86 emulator: add bsf/bsr instruction emulation Wei Yongjun
2010-08-10 3:14 ` Avi Kivity [this message]
2010-08-10 5:48 ` [PATCH v2] " Wei Yongjun
2010-08-10 10:21 ` Avi Kivity
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