[libvirt] Fwd: [PATCH] qemu: Add cmd_per_lun, max_sectors to virtio-scsi

Daniel P. Berrange berrange at redhat.com
Wed Jul 2 09:27:17 UTC 2014


On Tue, Jul 01, 2014 at 06:51:46PM -0700, Nicholas A. Bellinger wrote:
> Hi Mike & Co,
> 
> > ---------- Forwarded message ----------
> > From: Mike Perez <thingee at gmail.com>
> > Date: Fri, Jun 27, 2014 at 7:39 PM
> > Subject: Re: [libvirt] [PATCH] qemu: Add cmd_per_lun, max_sectors to
> > virtio-scsi
> > To: Ján Tomko <jtomko at redhat.com>
> > Cc: Eric Blake <eblake at redhat.com>, libvir-list at redhat.com,
> > berrange at redhat.com, "Nab at daterainc.com" <Nab at daterainc.com>
> > 
> > 
> > On Thu, Jun 5, 2014 at 6:57 AM, Ján Tomko <jtomko at redhat.com> wrote:
> > > On 05/23/2014 12:06 AM, Eric Blake wrote:
> > >> On 05/22/2014 12:22 PM, Mike Perez wrote:
> > >>> This introduces two new attributes "cmd_per_lun" and "max_sectors" same
> > >>> with the names QEMU uses for virtio-scsi. An example of the XML:
> > >>>
> > >>> <controller type='scsi' index='0' model='virtio-scsi' cmd_per_lun='50'
> > >>> max_sectors='512'/>
> > >>
> > >> I'm not a fan of underscore (why type the shift key, when a dash will
> > >> do).  The libvirt xml name does not have to exactly match the qemu
> > >> option name, so maybe there's some room for bikeshedding what names we
> > >> should actually present to the user.
> > >>
> > >
> > 
> > > IMO using underscores here would be consistent with other disk-related options
> > > like read_iops_sec; dashes are mostly used for network-related options.
> > >
> > > We could also use camelCase [1], or just roll a dice.
> > 
> > Well underscores are originally what I had in my first patch [1]. Eric
> > what do you think?
> > 
> 
> Can we please keep the libvirt names consistent for virtio-scsi
> parameters with what is already defined in qemu..?  (Paolo CC'ed)
> 
> From qemu/include/hw/virtio/virtio-scsi.h:
> 
> #define DEFINE_VIRTIO_SCSI_PROPERTIES(_state, _conf_field)                     \
>     DEFINE_PROP_UINT32("num_queues", _state, _conf_field.num_queues, 1),       \
>     DEFINE_PROP_UINT32("max_sectors", _state, _conf_field.max_sectors, 0xFFFF),\
>     DEFINE_PROP_UINT32("cmd_per_lun", _state, _conf_field.cmd_per_lun, 128)
> 
> AFAICT, having different names between qemu + libvirt parameters can
> only add confusion.

QEMU is not the only hypervisor that libvirt targets, so tieing libvirt
names to QEMU names is a non-goal. We pick the names that make most sense
in the context of libvirt.

Regards,
Daniel
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