Re: [Qemu-devel] [PATCH] spapr: Reduce advertised max LUNs for spapr_vscsi

[David Gibson <david@gibson.dropbear.id.au>]

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On Wed, Sep 09, 2015 at 08:25:34AM +0200, Thomas Huth wrote:
> On 09/09/15 03:22, David Gibson wrote:
> > The implementation of the PAPR paravirtual SCSI adapter currently
> > allows up to 32 LUNs (max_lun == 31).  However the adapter isn't really
> > designed to support lots of devices - the PowerVM implementation only
> > ever puts one disk per vSCSI controller.
> 
> Do you know how many LUNs are advertised by PowerVM?

Well, what do you mean by "advertised".  AFAIK from the point of view
of the guest, the number of LUNs is advertised per-target, not per
controller.

When I say "advertised" here, I'm meaning what the controller
advertises to the qemu SCSI core, and thereby to the option parsing
code.

> > More specifically, the Linux guest side vscsi driver (the only one we
> > really care about) is hardcoded to allow a maximum of 8 LUNs.
> 
> So what about changing the vscsi driver in Linux instead to support more
> LUNs?

Doesn't help for existing guests.  Basically what I'm trying to
achieve is for qemu to reject up-front configurations that are
unlikely to actually work in the guest.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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