Re: [Qemu-devel] [PATCH 2/3] scsi-disk: Add device_id property

[Peter Krempa <pkrempa@redhat.com>]

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On Mon, Jan 28, 2019 at 09:50:41 +0100, Peter Krempa wrote:
> On Fri, Jan 25, 2019 at 18:46:52 +0100, Kevin Wolf wrote:
> > The new device_id property specifies which value to use for the vendor
> > specific designator in the Device Identification VPD page.
> > 
> > In particular, this is necessary for libvirt to maintain guest ABI
> > compatibility when no serial number is given and a VM is switched from
> > -drive (where the BlockBackend name is used) to -blockdev (where the
> > vendor specific designator is left out by default).
> > 
> > Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> > ---
> >  hw/scsi/scsi-disk.c | 24 ++++++++++++++++--------
> >  1 file changed, 16 insertions(+), 8 deletions(-)
> 
> [...]
> 
> > @@ -2904,7 +2910,9 @@ static const TypeInfo scsi_disk_base_info = {
> >      DEFINE_PROP_STRING("ver", SCSIDiskState, version),               \
> >      DEFINE_PROP_STRING("serial", SCSIDiskState, serial),             \
> >      DEFINE_PROP_STRING("vendor", SCSIDiskState, vendor),             \
> > -    DEFINE_PROP_STRING("product", SCSIDiskState, product)
> > +    DEFINE_PROP_STRING("product", SCSIDiskState, product),           \
> > +    DEFINE_PROP_STRING("device_id", SCSIDiskState, device_id)
> 
> This adds the property only to 'scsi-disk', whereas libvirt will use
> 'scsi-cd' or 'scsi-hd' depending on the media type if the 'scsi-cd'
> device is detected. The following logic decides:
> 
> https://libvirt.org/git/?p=libvirt.git;a=blob;f=src/qemu/qemu_command.c;h=3e46f3ced3c1e6a4865e98e2d0cdce3214c4a5d2;hb=HEAD#l1978
> 
> This brings multiple questions:

I've found:

commit b443ae67130d32ad06b06fc9aa6d04d05ccd93ce
Author: Markus Armbruster <armbru@redhat.com>
Date:   Mon May 16 15:04:53 2011 +0200

    scsi: Split qdev "scsi-disk" into "scsi-hd" and "scsi-cd"

Which seems to put scsi-hd and scsi-cd as the thing to use.

Libvirt's code obviously did not adapt after that and we still keep to
probe scsi-disk instead of the split up devices, whereas we will never
use scsi-disk.

Also some of our tests seem to look as if scsi-disk was used which
confused me.

Since the new property is present also for scsi-hd and scsi-cd we really
need to adapt our code to that.

Btw, this also means that qemu can deprecate scsi-disk.

Sorry for the noise.

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