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[Qemu-devel] Re: [PATCH] new scsi-generic abstraction, use SG_IO


From: Avi Kivity
Subject: [Qemu-devel] Re: [PATCH] new scsi-generic abstraction, use SG_IO
Date: Wed, 18 Mar 2009 15:46:35 +0200
User-agent: Thunderbird 2.0.0.19 (X11/20090105)

Christoph Hellwig wrote:
Okay, I started looking into how to handle scsi-generic I/O in the
new world order.

I think the best is to use the SG_IO ioctl instead of the read/write
interface as that allows us to support scsi passthrough on disk/cdrom
devices, too.  See Hannes patch on the kvm list from August for an
example.

Now that we always do ioctls we don't need another abstraction than
bdrv_ioctl for the synchronous requests for now, and for asynchronous
requests I've added a aio_ioctl abstraction keeping it simple.

Long-term we might want to move the ops to a higher-level abstraction
and let the low-level code fill out the request header, but I'm lazy
enough to leave that to the people trying to support scsi-passthrough
on a non-Linux OS.

Tested lightly by issuing various sg_ commands from sg3-utils in a guest
to a host CDROM device.

I'm not familiar with SG_IO. Does it allow the device to dma to/from userspace?


--
error compiling committee.c: too many arguments to function





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