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Date: Wed, 6 May 2015 11:12:00 +0530
From: Bharata B Rao <bharata@linux.vnet.ibm.com>
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Subject: Re: [Qemu-devel] [RFC PATCH v3 18/24] xics_kvm: Don't enable
 KVM_CAP_IRQ_XICS if already enabled
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To: David Gibson <david@gibson.dropbear.id.au>
Cc: mdroth@linux.vnet.ibm.com, aik@ozlabs.ru, agraf@suse.de, qemu-devel@nongnu.org, qemu-ppc@nongnu.org, tyreld@linux.vnet.ibm.com, nfont@linux.vnet.ibm.com, imammedo@redhat.com, afaerber@suse.de

On Tue, May 05, 2015 at 05:22:52PM +1000, David Gibson wrote:
> On Fri, Apr 24, 2015 at 12:17:40PM +0530, Bharata B Rao wrote:
> > When supporting CPU hot removal by parking the vCPU fd and reusing
> > it during hotplug again, there can be cases where we try to reenable
> > KVM_CAP_IRQ_XICS CAP for the vCPU for which it was already enabled.
> > Introduce a boolean member in ICPState to track this and don't
> > reenable the CAP if it was already enabled earlier.
> > 
> > This change allows CPU hot removal to work for sPAPR.
> > 
> > Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> 
> Do you actually need this?  Is there any harm in setting the
> capability multiple times, or could you just ignore the "already set"
> error?

We discussed this last time and concluded that this patch is needed.

Ref: http://lists.nongnu.org/archive/html/qemu-devel/2015-03/msg05361.html

Regards,
Bharata.