Re: 4.7 qemu regression: HVM guests fail to boot from xvda

["Jan Beulich" <JBeulich@suse.com>]

>>> On 31.05.16 at 13:32, <george.dunlap@citrix.com> wrote:
> On Tue, May 31, 2016 at 12:16 PM, Olaf Hering <olaf@aepfle.de> wrote:
>> On Tue, May 31, George Dunlap wrote:
>>
>>> On Mon, May 30, 2016 at 9:42 PM, Olaf Hering <olaf@aepfle.de> wrote:
>>> > With staging-4.6 this domU boots from xvda, qemu creates an emulated
>>> > disk. With staging no disk is found, unless the name is changed to hda.
>>> > Looks like qemu-2.6 does not handle xvda either.
>>>
>>> This was intentional; see this thread:
>>>
>>> https://marc.info/?i=<1444820717-25565-1-git-send-email-anthony.perard@citrix.com>
>>>
>>> The idea was to make it possible to create an HVM guest with no
>>> emulated disks for guest booting with OVMF which contains PV drivers.
>>
>> This breaks the domU becasue it changes its device names from 'xvd' to
>> 'hd' if a xenlinux based kernel is used in domU.
>> In other words: every SUSE domU out there.
> 
> Sorry, can you expand on this a bit?  Are you saying that on SuSE, if
> you specify "vdev=xvda" in your config file, that you'll get PV
> devices named "/dev/xvda", but that if you specify "vdev=hda", that
> you'll get PV devices but named "/dev/hda"?

And just to clarify - this isn't really SUSE-specific, this is how the old
XenoLinux blkfront has always behaved. In fact when I saw this code
gone from the upstream (pv-ops) variant, I think I had inquired how
this is expected to be handling upgrade cases, and I don't think I got
much of a useful answer to that.

Jan


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