From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: From: Parav Pandit Date: Mon, 16 May 2022 21:08:34 +0000 Message-ID: References: <20220426225824.5918-1-mgurtovoy@nvidia.com> <20220426225824.5918-3-mgurtovoy@nvidia.com> <20220515111056-mutt-send-email-mst@kernel.org> In-Reply-To: <20220515111056-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Subject: [virtio-comment] RE: [PATCH v5 2/7] Introduce admin command set Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable To: "Michael S. Tsirkin" , Max Gurtovoy Cc: "jasowang@redhat.com" , "virtio-comment@lists.oasis-open.org" , "cohuck@redhat.com" , "virtio-dev@lists.oasis-open.org" , Oren Duer , Shahaf Shuler , "aadam@redhat.com" , "virtio@lists.oasis-open.org" List-ID: Hi Michael, > From: Michael S. Tsirkin > Sent: Sunday, May 15, 2022 11:24 AM [..] > > +\subsection{VIRTIO ADMIN DEVICE CAPS ACCEPT > command}\label{sec:Basic > > +Facilities of a Virtio Device / Admin command set / VIRTIO ADMIN > > +DEVICE CAPS ACCEPT command} > > + > > +The VIRTIO_ADMIN_DEVICE_CAPS_ACCEPT command is used by the > driver to acknowledge those admin capabilities it understands and wishes = to > use. >=20 >=20 > ok so we have a protocol here, kind of like feature negotiation. Please w= rite > its description. > e.g. is it ok to change accepted caps? when? can device change its caps e= tc > etc etc. >=20 > Avoiding this kind of spec work is exactly why me and jason keep telling = you > to consider just using features instead. Add a 64 bit admin features fiel= d to > the PCI transport and be done with it. CCW and MMIO already have feature > selector so it's trivial to add feature bits. >=20 As we begin to scale with the device, adding more and more registers like t= his demands more on-device real estate to comply to the PCI standards. And therefore, things are queried/accessed rare or occasionally, are better= accessed via a queue interface. One can argue that admin VQ is proposed only for the mgmt. functions so hav= ing this cfg register for PF is enough. However, AQ may find some usage in the VF/SF themselves down the road. Hence, keeping the cap exchange transport this way is more optimal. Max has called out this AQ rationale in 4 or 5 points in the cover letter. This publicly archived list offers a means to provide input to the=0D OASIS Virtual I/O Device (VIRTIO) TC.=0D =0D In order to verify user consent to the Feedback License terms and=0D to minimize spam in the list archive, subscription is required=0D before posting.=0D =0D Subscribe: virtio-comment-subscribe@lists.oasis-open.org=0D Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org=0D List help: virtio-comment-help@lists.oasis-open.org=0D List archive: https://lists.oasis-open.org/archives/virtio-comment/=0D Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf= =0D List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lis= ts=0D Committee: https://www.oasis-open.org/committees/virtio/=0D Join OASIS: https://www.oasis-open.org/join/