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Date: Tue, 28 Apr 2015 15:05:47 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v4 0/2] virtio: Move host features to
	backends
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: hangaohuai@huawei.com, "Huangpeng (Peter)" <peter.huangpeng@huawei.com>, QEMU Developers <qemu-devel@nongnu.org>, Shannon Zhao <shannon.zhao@linaro.org>, Shannon Zhao <zhaoshenglong@huawei.com>, Cornelia Huck <cornelia.huck@de.ibm.com>, Paolo Bonzini <pbonzini@redhat.com>, Christoffer Dall <christoffer.dall@linaro.org>

On Tue, Apr 28, 2015 at 01:52:40PM +0100, Peter Maydell wrote:
> On 28 April 2015 at 13:48, Michael S. Tsirkin <mst@redhat.com> wrote:
> > On Tue, Apr 28, 2015 at 07:51:11PM +0800, shannon.zhao@linaro.org wrote:
> >> From: Shannon Zhao <shannon.zhao@linaro.org>
> >> Here we move the host features to backends, involving
> >> DEFINE_VIRTIO_NET_FEATURES, DEFINE_VIRTIO_SCSI_FEATURES. So the
> >> virtio-mmio devices could have the host freatures, and this has a great
> >> performance improvement to virtio-mmio, especially to virtio-net-device.
> >
> > Can you move COMMON_FEATURES too please?
> 
> I think that would be wrong -- COMMON_FEATURES are transport features,
> not backend-specific features, so they belong on the transports
> (and on the convenience wrappers), not the backends.
> 
> thanks
> -- PMM

Hmm you are right. The problem is with s390 which
puts this DEFINE_VIRTIO_COMMON_FEATURES in all devices.