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From: Jeff Garzik <jeff@garzik.org>
To: Jon Mason <jdmason@us.ibm.com>
Cc: Andi Kleen <ak@suse.de>, Muli Ben-Yehuda <muli@il.ibm.com>,
	Muli Ben-Yehuda <mulix@mulix.org>,
	Linux-Kernel <linux-kernel@vger.kernel.org>,
	discuss@x86-64.org, Andrew Morton <akpm@osdl.org>
Subject: Re: [PATCH 2/4] x86-64: Calgary IOMMU - move valid_dma_direction into the callers
Date: Thu, 25 May 2006 00:35:07 -0400	[thread overview]
Message-ID: <447533FB.1080400@garzik.org> (raw)
In-Reply-To: <20060525033550.GD7720@us.ibm.com>

Jon Mason wrote:
>>From Andi Kleen's comments on the original Calgary patch, move
> valid_dma_direction into the calling functions.
> 
> Signed-off-by: Muli Ben-Yehuda <muli@il.ibm.com>
> Signed-off-by: Jon Mason <jdmason@us.ibm.com>

Even though BUG_ON() includes unlikely(), this introduces additional 
tests in very hot paths.

_Why_ do we need this at all?

I would prefer to NAK the patch, and fix the odd user that gets it 
wrong.  It becomes REALLY obvious that a driver has gotten this wrong, 
REALLY quickly.

I see no need to burden critical hot paths with dumb checks like this.

	Jeff




  reply	other threads:[~2006-05-25  4:35 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-05-25  3:35 [PATCH 2/4] x86-64: Calgary IOMMU - move valid_dma_direction into the callers Jon Mason
2006-05-25  4:35 ` Jeff Garzik [this message]
2006-05-25  9:42   ` Muli Ben-Yehuda
2006-05-25  9:58     ` Jeff Garzik
2006-05-26  7:57       ` [discuss] " Andi Kleen
2006-05-26  8:55         ` Jeff Garzik
2006-05-26  9:35           ` Andi Kleen

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