From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andi Kleen <andi@firstfloor.org>
Subject: Re: [PATCH] x86_emulate: Emulate nop (0x90) instruction
Date: Sat, 14 Jun 2008 15:26:36 +0200
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Cc: kvm@vger.kernel.org, avi@qumranet.com, riel@surriel.com
To: "Mohammed Gamal" <m.gamal005@gmail.com>
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In-Reply-To: <52d4a3890806140450k14a13025i3dd3a60187940804@mail.gmail.com> (Mohammed Gamal's message of "Sat, 14 Jun 2008 14:50:59 +0300")
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"Mohammed Gamal" <m.gamal005@gmail.com> writes:
>  	ByteOp | DstReg | SrcMem | Mov | MemAbs, DstReg | SrcMem | Mov | MemAbs,
> @@ -1560,6 +1560,9 @@ special_insn:
>  		if (rc != 0)
>  			goto done;
>  		break;
> +	case 0x90: /* nop */
> +		if(! (c->rex_prefix & 1) )
> +			break;
>  	case 0x9c: /* pushf */
>  		c->src.val =  (unsigned long) ctxt->eflags;
>  		emulate_push(ctxt);

Is falling through to pushf really correct?  And not sure what the if checks.

iirc it should be just

     case 0x90: /* nop */
          break;

BTW there are lots more nop encodings.

-Andi