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From: "H. Peter Anvin" <hpa@zytor.com>
To: Klemen Jan Enova <klemen.jan.enova@gmail.com>,
	linux-kernel@vger.kernel.org
Cc: mingo@redhat.com, x86@kernel.org
Subject: Re: [PATCH] arch: x86: boot: bioscall.S: simplify self-modification of the INT instruction
Date: Tue, 22 Jul 2014 04:25:53 -0700	[thread overview]
Message-ID: <53CE4A41.4020605@zytor.com> (raw)
In-Reply-To: <53CE449C.2090001@gmail.com>

On 07/22/2014 04:01 AM, Klemen Jan Enova wrote:
> At the start of the intcall function, the %al register is compared to
> 0x3f. If it does not equal 0x3f it is equated to it. Instruction flow
> continues in both cases from the label 1. The comparison is therefore
> unneeded.
> 
> Testing data is appended.
> 
> Signed-off-and-tested-by: Klemen Jan Enova <klemen.jan.enova@gmail.com>

NAK.

This is a performance optimization - the SMC takes a substantial penalty
so the write is avoided if necessary.

Also, 3f is a label, not 0x3f.

	-hpa


      reply	other threads:[~2014-07-22 11:26 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-07-22 11:01 [PATCH] arch: x86: boot: bioscall.S: simplify self-modification of the INT instruction Klemen Jan Enova
2014-07-22 11:25 ` H. Peter Anvin [this message]

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