linux-kernel - Re: [PATCH] vfio: Enable VFIO device for powerpc

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Message-ID: <55ED6FC1.60205@redhat.com>
Date:	Mon, 7 Sep 2015 13:06:41 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Paul Mackerras <paulus@...abs.org>, Alexander Graf <agraf@...e.de>
Cc:	David Gibson <david@...son.dropbear.id.au>,
	alex.williamson@...hat.com, aik@...abs.ru,
	mdroth@...ux.vnet.ibm.com, benh@...nel.crashing.org,
	mpe@...erman.id.au, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, kvm-ppc <kvm-ppc@...r.kernel.org>
Subject: Re: [PATCH] vfio: Enable VFIO device for powerpc



On 26/08/2015 20:54, Paul Mackerras wrote:
> On Wed, Aug 26, 2015 at 11:34:26AM +0200, Alexander Graf wrote:
>>
>>
>> On 13.08.15 03:15, David Gibson wrote:
>>> ec53500f "kvm: Add VFIO device" added a special KVM pseudo-device which is
>>> used to handle any necessary interactions between KVM and VFIO.
>>>
>>> Currently that device is built on x86 and ARM, but not powerpc, although
>>> powerpc does support both KVM and VFIO.  This makes things awkward in
>>> userspace
>>>
>>> Currently qemu prints an alarming error message if you attempt to use VFIO
>>> and it can't initialize the KVM VFIO device.  We don't want to remove the
>>> warning, because lack of the KVM VFIO device could mean coherency problems
>>> on x86.  On powerpc, however, the error is harmless but looks disturbing,
>>> and a test based on host architecture in qemu would be ugly, and break if
>>> we do need the KVM VFIO device for something important in future.
>>>
>>> There's nothing preventing the KVM VFIO device from being built for
>>> powerpc, so this patch turns it on.  It won't actually do anything, since
>>> we don't define any of the arch_*() hooks, but it will make qemu happy and
>>> we can extend it in future if we need to.
>>>
>>> Signed-off-by: David Gibson <david@...son.dropbear.id.au>
>>> Reviewed-by: Eric Auger <eric.auger@...aro.org>
>>
>> Paul is going to take care of the kvm-ppc tree for 4.3. Also, ppc kvm
>> patches should get CC on the kvm-ppc@...r mailing list ;).
>>
>> Paul, could you please pick this one up?
> 
> Sure, I'll do that once I get home (end of this week).

This was not in the 4.3 pull request, but I think we can apply it after
the end of the merge window.

Paolo
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