Re: [Qemu-devel] [PATCH v2] spapr_drc: don't allow 'empty' DRCs to be unisolated

[Bharata B Rao <bharata@linux.vnet.ibm.com>]

On Tue, Sep 08, 2015 at 06:44:55PM -0500, Michael Roth wrote:
> Logical resources start with allocation-state:UNUSABLE /
> isolation-state:ISOLATED. During hotplug, guests will transition
> them to allocate-state:USABLE, and then to isolate-state:UNISOLATED.
> The former transition does not seem to have any failure path for
> cases where a DRC does not have any resources associated with it to
> allocate for guest, but instead relies on the subsequent
> isolation-state:UNISOLATED transition to indicate failure in this
> situation.
> 
> Currently DRC code does not implement this logic, but instead
> tries to indicate failure by refusing the allocation-state:USABLE
> transition. Unfortunately, since that's not a documented failure
> path, guests continue undeterred, causing undefined behavior in
> QEMU and guest code.
> 
> Fix this by handling things as PAPR defines (13.7 and 13.7.3.1).
> 
> Cc: qemu-ppc@nongnu.org
> Cc: David Gibson <david@gibson.dropbear.id.au>
> Cc: Bharata B Rao <bharata@linux.vnet.ibm.com>
> Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

Tested-by: Bharata B Rao <bharata@linux.vnet.ibm.com>