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Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS
From: |
Samuel Thibault |
Subject: |
Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS |
Date: |
Thu, 26 Mar 2009 19:48:14 +0100 |
User-agent: |
Mutt/1.5.12-2006-07-14 |
Avi Kivity, le Thu 26 Mar 2009 20:32:28 +0200, a écrit :
> Samuel Thibault wrote:
> >Avi Kivity, le Thu 26 Mar 2009 14:58:55 +0200, a écrit :
> >>Samuel Thibault wrote:
> >>>it should be centralized in the block layer instead of placing the
> >>>burden on all block format drivers ;)
> >>>
> >>If other drivers need to do that, certainly.
> >
> >In our case the other driver is specific to Xen.
>
> I'm confused. I can only count one driver which has limited dma size.
Then you are not looking at the same place as I am. The Xen tree is at
http://xenbits.xensource.com/git-http/qemu-xen-unstable.git
> >>>One thing for instance that still have been overlooked although patches
> >>>have been sent is block-raw-posix' read/write_pread_aligned() that
> >>>consider partial read/writes as an error. That's a bug.
> >>>
> >>Right. Unrelated topic though?
> >
> >Nope. It's exactly the issue: read/write() may not be able to perform
> >the whole operation in just one go, and qemu should continue in that
> >case.
>
> Oh, you're overloading block-raw-posix?
I'm not. Actually, I am _also_ implementing the read/write() functions,
but that's another matter. In the xen tree, there is an addition
block-vbd.c driver. I'm here just pointing out that the problem is not
_only_ in the xen-specific driver, but also in the posix driver, on any
OS that doesn't necessarily do all the work the caller asked for (which
is _allowed_ by POSIX).
> Isn't it more natural for you to implement
> block-raw-xen-pv-block-frontend?
That's it.
> You'd be able to use asynchronous requests instead of a thread pool
> (much like block-raw-linux-aio).
That's it. But the xen ring protocols limits the amount of data
transferred at a time, thus the limitation.
Samuel
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, (continued)
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, Avi Kivity, 2009/03/26
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, Stefano Stabellini, 2009/03/26
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, Avi Kivity, 2009/03/26
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, Stefano Stabellini, 2009/03/26
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, Avi Kivity, 2009/03/26
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, Stefano Stabellini, 2009/03/26
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, Samuel Thibault, 2009/03/26
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, Avi Kivity, 2009/03/26
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, Samuel Thibault, 2009/03/26
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, Avi Kivity, 2009/03/26
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS,
Samuel Thibault <=
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, Avi Kivity, 2009/03/26
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, Samuel Thibault, 2009/03/26
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, Avi Kivity, 2009/03/27
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, Samuel Thibault, 2009/03/27
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, Avi Kivity, 2009/03/27
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, Samuel Thibault, 2009/03/27
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, Christoph Hellwig, 2009/03/26
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, Samuel Thibault, 2009/03/26
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, Avi Kivity, 2009/03/27
- Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS, Samuel Thibault, 2009/03/27