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Date: Wed, 17 Jun 2015 15:46:39 +0200
From: Aurelien Jarno <aurelien@aurel32.net>
Message-ID: <20150617134639.GD19635@aurel32.net>
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Subject: Re: [Qemu-devel] [PATCH] s390x: Switch to s390-ccw machine as
	default
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To: Alexander Graf <agraf@suse.de>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>, Christian Borntraeger <borntraeger@de.ibm.com>, qemu-devel@nongnu.org

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.

Aurelien

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                 http://www.aurel32.net