Re: [PATCH 1/2] virtio-scsi: first version

From: Paolo Bonzini
Date: Sat Dec 03 2011 - 12:38:13 EST


On 12/03/2011 12:07 AM, Benjamin Herrenschmidt wrote:
This is typically the one thing you should -really- obtain from the
other side. This is the number one reason why we cannot today reliably
emulate a SCSI controller in qemu -and- pass-through the SCSI commands
to the host /dev/sg or equivalent (only full device emulation is
reliable).

This is also typically what something like virtio-scsi allows us to fix,
so let's fix it. IE. we have the ability to query the "limits" of the
real HBA / transport on the host side and to pass them along to the
guest, which enables us to do real pass-through.

You can fix this in QEMU; READ and WRITE commands can be split in multiple parts. The scsi-block device I added recently does this.

However, it seems like a simple change, so I'll do it. I'll add max_sectors and cmd_per_lun to the config space.

Paolo
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