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Tsirkin" To: Max Gurtovoy Cc: virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, stefanha@redhat.com, oren@nvidia.com, nitzanc@nvidia.com Subject: Re: [PATCH 1/1] virtio: add VIRTIO_F_IN_ORDER to header file Message-ID: <20210905110804-mutt-send-email-mst@kernel.org> References: <20210905120911.8239-1-mgurtovoy@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210905120911.8239-1-mgurtovoy@nvidia.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Sun, Sep 05, 2021 at 03:09:11PM +0300, Max Gurtovoy wrote: > For now only add this definition from the spec. In the future, The > drivers should negotiate this feature to optimize the performance. > > Signed-off-by: Max Gurtovoy So I think IN_ORDER was a mistake since it breaks ability to do pagefaults efficiently without stopping the ring. I think that VIRTIO_F_PARTIAL_ORDER is a better option - am working on finalizing that proposal, will post RSN now. > --- > include/uapi/linux/virtio_config.h | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/include/uapi/linux/virtio_config.h b/include/uapi/linux/virtio_config.h > index b5eda06f0d57..3fcdc4ab6f19 100644 > --- a/include/uapi/linux/virtio_config.h > +++ b/include/uapi/linux/virtio_config.h > @@ -82,6 +82,12 @@ > /* This feature indicates support for the packed virtqueue layout. */ > #define VIRTIO_F_RING_PACKED 34 > > +/* > + * This feature indicates that all buffers are used by the device in the same > + * order in which they have been made available. > + */ > +#define VIRTIO_F_IN_ORDER 35 > + > /* > * This feature indicates that memory accesses by the driver and the > * device are ordered in a way described by the platform. > -- > 2.18.1