From: Christoph Hellwig <hch@lst.de>
To: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH 1/3] Add specialized block driver scsi generic API
Date: Sun, 15 Mar 2009 16:06:34 +0100 [thread overview]
Message-ID: <20090315150634.GA32019@lst.de> (raw)
In-Reply-To: <49BD1771.9040905@redhat.com>
On Sun, Mar 15, 2009 at 04:57:53PM +0200, Avi Kivity wrote:
> Christoph Hellwig wrote:
> >The patch series (now posted) makes all aio APIs use iovecs. The
> >current non-iovec based SG API would require some nasty shims allocating
> >nested aiocbs. Or we could just make the sg aio methods fake-ioveced
> >which is the solution I had before your split, always adding a
> >one-element iovec to the scsi-generic request structure.
> >
>
> I'd go for having everything vectored. It's how non-1962 hardware works.
Yeah, that's what I did for regular block I/O in my series.
scsi-generic is a little different beast, though. qemu uses the legacy
(not sure if it's formally deprecated) read/write support on /dev/sg
which doen't support vectored I/O. If we want to use vectored I/O
with sg we'd have to use the SG_IO ioctl (which also has the advantage
of working with all sd/sr/ide/etc block devices). But supporting that
would probably require very different APIs then the current (aio-)
read/writeish one.
next prev parent reply other threads:[~2009-03-15 15:06 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-12 12:57 [Qemu-devel] [PATCH 0/3] Remove ->bdrv_pread() internal block layer API (v2) Avi Kivity
2009-03-12 12:57 ` [Qemu-devel] [PATCH 1/3] Add specialized block driver scsi generic API Avi Kivity
2009-03-14 14:33 ` Christoph Hellwig
2009-03-15 13:54 ` Avi Kivity
2009-03-15 14:43 ` Christoph Hellwig
2009-03-15 14:57 ` Avi Kivity
2009-03-15 15:06 ` Christoph Hellwig [this message]
2009-03-16 17:29 ` Jamie Lokier
2009-03-12 12:57 ` [Qemu-devel] [PATCH 2/3] Add internal scsi generic block API Avi Kivity
2009-03-12 12:57 ` [Qemu-devel] [PATCH 3/3] Drop internal bdrv_pread()/bdrv_pwrite() APIs Avi Kivity
2009-03-12 19:57 ` [Qemu-devel] Re: [PATCH 0/3] Remove ->bdrv_pread() internal block layer API (v2) Anthony Liguori
-- strict thread matches above, loose matches on Subject: below --
2009-02-08 17:59 [Qemu-devel] [PATCH 0/3] Remove ->bdrv_pread() internal block layer API Avi Kivity
2009-02-08 17:59 ` [Qemu-devel] [PATCH 1/3] Add specialized block driver scsi generic API Avi Kivity
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