From mboxrd@z Thu Jan 1 00:00:00 1970 From: Victor Kaplansky Subject: Re: [PATCH v2 1/2] virtio-net: rephrase devconf fields description Date: Wed, 19 Aug 2015 14:54:37 +0300 Message-ID: <20150819143550-mutt-send-email-victork@redhat.com> References: <1439732494-29765-1-git-send-email-victork@redhat.com> <1439732494-29765-2-git-send-email-victork@redhat.com> <55D14A62.2060408@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: virtio-dev@lists.oasis-open.org, mst@redhat.com, netdev@vger.kernel.org, virtualization@lists.linux-foundation.org To: Jason Wang Return-path: Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Content-Disposition: inline In-Reply-To: <55D14A62.2060408@redhat.com> List-Id: netdev.vger.kernel.org On Mon, Aug 17, 2015 at 10:43:46AM +0800, Jason Wang wrote: > > > On 08/16/2015 09:42 PM, Victor Kaplansky wrote: > > Clarify general description of the mac, status and > > max_virtqueue_pairs fields. Specifically, the old description is > > vague about configuration layout and fields offsets when some of > > the fields are non valid. > > > > Also clarify that validity of two status bits depends on two > > different feature flags. > > > > Signed-off-by: Victor Kaplansky > > --- > > + > > +\item [\field{max_virtqueue_pairs}] tells the driver the maximum > > + number of each of virtqueues (receiveq1\ldots receiveqN and > > + transmitq1\ldots transmitqN respectively) that can be configured > > + on the device once VIRTIO_NET_F_MQ is negotiated. > > + \field{max_virtqueue_pairs} is valid only if VIRTIO_NET_F_MQ is > > + set and can be read by the driver. > > + > > > I don't get the point that adding "can be read by the driver". Looks > like it's hard for hypervisor to detect this? AFAIU, if the device sets VIRTIO_NET_F_MQ, the device also sets the value of 'max_virtqueue_pairs' even before driver negotiated VIRTIO_NET_F_MQ. If so, the driver can read the value of 'max_virtqueue_pairs' during negotiation and potentially this value can even affect negotiation decision of the driver. If above is correct, I'll change the description to make this point more clear. Thanks, -- Victor