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From: Takuya Yoshikawa <takuya.yoshikawa@gmail.com>
To: Avi Kivity <avi@redhat.com>
Cc: mtosatti@redhat.com, kvm@vger.kernel.org, yoshikawa.takuya@oss.ntt.co.jp
Subject: Re: [PATCH 4/4] KVM: x86 emulator: Avoid pushing back ModRM byte in decode_opcode()
Date: Tue, 24 Apr 2012 23:27:36 +0900	[thread overview]
Message-ID: <20120424232736.91d7c5fe3ae27393ac41f36d@gmail.com> (raw)
In-Reply-To: <4F96B440.1030106@redhat.com>

On Tue, 24 Apr 2012 17:10:08 +0300
Avi Kivity <avi@redhat.com> wrote:

> > +	if (!modrm_fetched && (ctxt->d & ModRM))
> > +		ctxt->modrm = insn_fetch(u8, ctxt);
> 
> Instead of adding yet another conditional, how about doing something like
> 
>    if ((c->d & ModRM) || (gtype == Group) || (gtype == GroupDual))
>           ctxt->modrm = insn_fetch(u8, ctxt);
> 
> somewhere early?

Looks nicer than mine.

> In fact even that is too much.  All groups have ModRM somewhere in their
> encoding; all we have to do is move it to the main tables (opcode_table
> or twobyte_table) and just move the existing modrm fetch before group
> parsing.

I see.

Then, the best way to go seems to be drop patch-4 and work on the ModRM
fetch issue separately.

Modifying the tables needs some care.

Thanks,
	Takuya

  reply	other threads:[~2012-04-24 14:27 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-04-23 15:31 [PATCH 0/4] KVM: x86 emulator: Split decoder into separate functions Takuya Yoshikawa
2012-04-23 15:33 ` [PATCH 1/4] KVM: x86 emulator: Introduce ctxt->op_prefix for 0x66 prefix Takuya Yoshikawa
2012-04-23 15:34 ` [PATCH 2/4] KVM: x86 emulator: Make prefix decoding a separate function Takuya Yoshikawa
2012-04-23 15:35 ` [PATCH 3/4] KVM: x86 emulator: Make opcode " Takuya Yoshikawa
2012-04-23 15:37 ` [PATCH 4/4] KVM: x86 emulator: Avoid pushing back ModRM byte in decode_opcode() Takuya Yoshikawa
2012-04-24 14:10   ` Avi Kivity
2012-04-24 14:27     ` Takuya Yoshikawa [this message]
2012-04-24 14:11 ` [PATCH 0/4] KVM: x86 emulator: Split decoder into separate functions Avi Kivity
2012-04-24 14:41   ` Takuya Yoshikawa

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