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Date: Wed, 16 Oct 2013 08:36:10 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] virtio-blk-pci: how to tell if it is CD or HDD?
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To: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: "Michael S. Tsirkin" <mst@redhat.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>, Alex Graf <agraf@suse.de>

Il 16/10/2013 07:04, Alexey Kardashevskiy ha scritto:
> Hi!
> 
> Normally on sPAPR platform the IBMVSCSI host bus adapter is used which is
> SCSI. So when we want some image to appear as a DVD to the guest
> (particularly SLOF - our firmware), we use "-device scsi-cd". Or QEMU
> extracts this automatically from the "media=cdrom" property of "-drive"
> (correct?). And then the SCSI bus tells the guest what is what. SLOF
> firmware uses this to create "disk" and "cdrom" aliases to correcly apply
> the boot order. So far so good.
> 
> Now we are trying (via libvirt) to add both HDD and DVD as "virtio-blk-pci"
> devices:
> 
> -drive file=virtimg/rhel6-root.img,if=none,format=raw,\
> id=drive-virtio-disk1,cache=none \
> -device virtio-blk-pci,bus=pci,addr=0x4,\
> drive=drive-virtio-disk1,id=virtio-disk1,bootindex=2 \
> \
> -drive file=virtimg/SLES-11-SP3-DVD-ppc64-GM-DVD1.iso,\
> if=none,media=cdrom,id=drive-virtio-disk2,readonly=on,\
> format=raw\
> -device virtio-blk-pci,bus=pci,addr=0x5,\
> drive=drive-virtio-disk2,id=virtio-disk2,bootindex=1
> 
> No SCSI bus is created in this case. Both devices appear to SLOF as HDDs so
> it creates just one "disk" alias and no "cdrom" alias and if we are not
> lucky and DVD got bigger PCI slot#, we will never be able to boot from DVD.
> 
> Is there any way to distinguish HDD from DVD via virtio protocol from the
> guest (i.e. SLOF)? Thanks!

No, virtio-blk is always a HDD.

Does bootindex work with pSeries?

Paolo