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Date: Wed, 05 Dec 2007 08:47:32 -0600
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] [PATCH 2/2 v2] Direct IDE I/O
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To: qemu-devel@nongnu.org

Gerd Hoffmann wrote:
> Anthony Liguori wrote:
>   
>> Gerd Hoffmann wrote:
>>     
>   Hi,
>
>   
>> I really want to use readv/writev though.  With virtio, we get a
>> scatter/gather list for each IO request.
>>     
>
> Yep, I've also missed pwritev (or whatever that syscall would be named).
>
>   
>> Once I post the virtio-blk driver, I'll follow up a little later with
>> some refactoring of the block device layers.  I think it can be made
>> much simpler while still remaining asynchronous.
>>
>>     
>>> IMHO the only alternative to that scheme would be to turn the block
>>> drivers in some kind of remapping drivers for the various file formats
>>> which don't actually perform the I/O.  Then you can handle the actual
>>> I/O in a generic way using whatever API is available, be it posix-aio,
>>> linux-aio or slow-sync-io.
>>>       
>> That's part of my plan.
>>     
>
> Oh, cool.  Can you also turn them into a sane shared library while being
> at it?  The current approach to compile it once for qemu and once for
> qemu-img with -DQEMU_TOOL isn't that great.  But if you factor out the
> actual I/O the block-raw.c code should have no need to mess with qemu
> internals any more and become much cleaner and simpler ...
>   

Yeah, it is definitely something that should be turned into a shared 
library.  I don't think I'll attempt that at first but I do agree it's 
the right direction to move toward.

Regards,

Anthony Liguori

> cheers,
>   Gerd
>
>
>
>
>