scsi passthrough differs between guests

[daggs]

Greetings Peter,

> Sent: Thursday, October 15, 2020 at 2:01 PM
> From: "Peter Krempa" <pkrempa at redhat.com>
> To: "daggs" <daggs at gmx.com>
> Cc: "libvirt-usersredhat.com" <libvirt-users at redhat.com>
> Subject: Re: scsi passthrough differs between guests
>
> [...]
>
> > -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.
the "good" syntax was created with libvirt of version which is earlier than 6.7, libvirt was upgraded several times since the vm creation.
I don't know if the syntax is changed every version or not.

>
> 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.
>
>

my system is gentoo, hence, every pkg is compiled, if you provide a patch, I can test it easily.

Thanks for the effort,

Dagg.