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Re: [Qemu-devel] [PATCH 6/6] ide: Avoid canceling IDE DMA

From: Kevin Wolf
Subject: Re: [Qemu-devel] [PATCH 6/6] ide: Avoid canceling IDE DMA
Date: Fri, 18 Mar 2011 12:34:09 +0100
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20101027 Fedora/3.0.10-1.fc12 Thunderbird/3.0.10

Am 18.03.2011 12:19, schrieb Christoph Hellwig:
> On Tue, Aug 03, 2010 at 04:44:30PM +0200, Kevin Wolf wrote:
>> Furthermore because the DMA operation is splitted into many synchronous
>> aio_read/write if there's more than one entry in the SG table, without this
>> patch the DMA would be cancelled in the middle, something we've no idea if it
>> happens on real hardware too or not. Overall this seems a great risk for zero
>> gain.
> That hasn't been true for a long time when this code was commited, at least
> on kernel supporting preadv/pwritev and/or aio.

So what do you want to tell us? Should the patch be reverted?

I think the request can still be split in multiple bdrv_aio_readv/writev
calls in dma-helpers.c and in non-raw block drivers, so we would still
cancel somewhere in the middle.


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