Re: [Qemu-devel] [PATCH] s390x: Switch to s390-ccw machine as default

[Christian Borntraeger]

Am 17.06.2015 um 15:46 schrieb Aurelien Jarno:
> On 2015-06-16 23:08, Alexander Graf wrote:
>> We now finally have TCG support for the basic set of instructions necessary
>> to run the s390-ccw machine. That means in any aspect possible that machine
>> type is now superior to the legacy s390-virtio machine.
>>
>> Switch over to the ccw machine as default. That way people don't get a 
>> halfway
>> broken machine with the s390x target.
> 
> It seems the current s390x-ccw firmware doesn't allow to boot on a
> virtio-scsi-ccw disk (but this is not a regression compared to the
> s390-virtio machine). virtio-scsi has some advantages over virtio-blk,
> like the possibility to do thin-provisioning. Of course one can use a
> small virtio-blk for the /boot partition, and virtio-scsi for the
> remaining disks.
> 
> Do you think it would possible to add it? Given a virtio-scsi device can
> provide multiple disks, how can we pass the disk to boot on to the
> firmware? Currently it seems we pass the ccw device in GR7, but not more
> details.

Yes, we look into that, Integrating this into s390 specifics without adding
hacks that have to last forever will take most of the time. We have to 
consider aspects like loadparm, the existing interfaces for the zfcp
connectivity in the diag308 handler and so on (so that /sys/firmware/ipl/
reflects the disks) - so give us some time to do it properly to see
how this can be integrated.

Christian