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Date: Fri, 27 Mar 2009 11:36:28 +0100
From: Samuel Thibault <samuel.thibault@ens-lyon.org>
Subject: Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS
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To: qemu-devel@nongnu.org

Avi Kivity, le Fri 27 Mar 2009 13:02:49 +0300, a écrit :
> Samuel Thibault wrote:
> >Nothing in Linux makes filesystems and devices systematically read/write
> >the amount of data that was requested.
> 
> We're talking about the qemu block layer, not Linux.

Well, in the part I quoted before my sentence:

> At least for Linux I couldn't think of a way to introduce such an
> arbitrary limit anyway.

I believed you were talking about Linux never making short reads.

> You're proposing to take the posix API rules and apply them to the
> qemu block layer.

No.  I'm proposing to take into account that because of the posix API
rules, we should fix our block layer.

> But posix read/write does not fit how DMA works.  A request should
> either complete fully, or fail, leaving the destination (disk or
> memory) in an undefined state.

Sure.  Again, please read what _I_ wrote: I'm not proposing to expose
that into DMA, just make it genericly handled in the block layer.

Samuel