Re: scsi passthrough differs between guests
On Thu, Oct 15, 2020 at 12:36:08 +0200, daggs wrote:
Greetings Peter,
> Sent: Thursday, October 15, 2020 at 9:52 AM
> From: "Peter Krempa" <pkrempa(a)redhat.com>
> To: "daggs" <daggs(a)gmx.com>
> Cc: "libvirt-usersredhat.com" <libvirt-users(a)redhat.com>
> Subject: Re: scsi passthrough differs between guests
>
> I don't see anything wrong with you configs. There were some changes
> related to SCSI hostdevs, between 6.7.0 an 6.8.0, but none of them
> should actually impact that use case.
>
> Said that, could you please post the actual qemu command lines that
> libvirt formatted for the two VMs you mention above.
>
> The command line can be found in /var/log/libvirt/qemu/$VMNAME.log .
> Please make sure you post the latest/actual one. It'll help showing
> whether anything changed between the two or there is a different
> problem.
>
here is the good cmd:
/usr/bin/qemu-system-x86_64 \
[...]
-drive file=/dev/sg5,if=none,format=raw,id=drive-hostdev0,readonly=on
\
-device
scsi-generic,bus=scsi0.0,channel=0,scsi-id=0,lun=0,drive=drive-hostdev0,id=hostdev0 \
[...]
the bad one:
/usr/bin/qemu-system-x86_64 \
[...]
-blockdev
'{"driver":"host_device","filename":"/dev/sg0","node-name":"libvirt-hostdev0-backend","read-only":true}'
\
-device
scsi-generic,bus=scsi0.0,channel=0,scsi-id=0,lun=0,drive=libvirt-hostdev0-backend,id=hostdev0
\
This doesn't corelate with the version numbers you've mentioned, because
the "new" syntax which uses -blockdev was present both in 6.7.0 and
6.8.0.
Anyways the problem is almost certainly that the hostdev code doesn't
detect that it's a cdrom. We have such a hack in the disk code which
turns a 'host_device' into a 'host_cdrom'. I'll try fixing it but I
don't have a machine with a cdrom handy, so it would be nice if you
could test it afterwards.
Thanks for the report.