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Re: [Qemu-devel] buffer alignment for block backends
From: |
Stefano Stabellini |
Subject: |
Re: [Qemu-devel] buffer alignment for block backends |
Date: |
Thu, 09 Apr 2009 14:30:31 +0100 |
User-agent: |
Thunderbird 2.0.0.14 (X11/20080505) |
Anthony Liguori wrote:
>> my backend (block-vbd) needs page aligned buffers because blkfront needs
>> page aligned buffers. I could allocate a new page aligned buffer every
>> time and the memcpy but it is just a waste.
>>
>
> You'll need to check the alignment of the request and bounce it if
> necessary. In the case that you have zero-copy requests coming from the
> guest that aren't page aligned, someone has to bounce the thing to make
> it page aligned.
Yes, but that is exactly what I was trying to avoid.
I can provide a bounce buffer fallback anyway (I actually should) but I
would really like to avoid using it.
> So I presume you're implementing blkfront in userspace? Does minios
> provide a userspace interface for grant tables that looks similar to the
> interfaces on Linux? Were you planning on submitting this for inclusion
> in upstream QEMU?
The userspace\kernelspace distinction does not make much sense in
minios, but yes it provides an interface to communicate with blkback in
dom0. This interface is used by block-vbd in qemu instead of
block-raw-posix when run in minios.
> I think it's a reasonable thing to include provided it's relatively
> self-contained.
>
good!
- [Qemu-devel] buffer alignment for block backends, Stefano Stabellini, 2009/04/08
- Re: [Qemu-devel] buffer alignment for block backends, Anthony Liguori, 2009/04/08
- Re: [Qemu-devel] buffer alignment for block backends, Stefano Stabellini, 2009/04/09
- Re: [Qemu-devel] buffer alignment for block backends, Anthony Liguori, 2009/04/09
- Re: [Qemu-devel] buffer alignment for block backends,
Stefano Stabellini <=
- Re: [Qemu-devel] buffer alignment for block backends, Gerd Hoffmann, 2009/04/09
- Re: [Qemu-devel] buffer alignment for block backends, Samuel Thibault, 2009/04/09
- Re: [Qemu-devel] buffer alignment for block backends, Stefano Stabellini, 2009/04/09
- Re: [Qemu-devel] buffer alignment for block backends, Gerd Hoffmann, 2009/04/09
- Re: [Qemu-devel] buffer alignment for block backends, Stefano Stabellini, 2009/04/09
- Re: [Qemu-devel] buffer alignment for block backends, Samuel Thibault, 2009/04/09
- Re: [Qemu-devel] buffer alignment for block backends, Anthony Liguori, 2009/04/09
- Re: [Qemu-devel] buffer alignment for block backends, Jamie Lokier, 2009/04/09
- Re: [Qemu-devel] buffer alignment for block backends, Samuel Thibault, 2009/04/09
- Re: [Qemu-devel] buffer alignment for block backends, Lennart Sorensen, 2009/04/09