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Re: [Qemu-devel] [PATCH 2/3] target-i386/translate.c: mov to/from crN/dr

From: malc
Subject: Re: [Qemu-devel] [PATCH 2/3] target-i386/translate.c: mov to/from crN/drN: ignore mod bits
Date: Sat, 28 Jul 2012 00:53:33 +0400 (MSK)
User-agent: Alpine 2.00 (LNX 1167 2008-08-23)

On Fri, 27 Jul 2012, Matthew Ogilvie wrote:

> Microport UNIX System V/386 v 2.1 (ca 1987) uses mod R/M bytes for
> the control register mov instructions where the mod bits are 0,
> even though the 80386 spec claims they are "always" 1's.  The fact
> that it ran at all clearly indicates the real chips (at least 386
> and 486) just ignores the bits and assumes they are 1's, rather
> than trigger an illegal instruction if they aren't.

AMD's document is explicit about it:

This instruction is always treated as a register-to-register (MOD = 11)
instruction, regardless of the encoding of the MOD field in the MODR/M

24594.pdf page 316

So i belive this patch should just be applied, thanks.



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