From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id 63C789865AB for ; Wed, 22 Feb 2023 13:26:56 +0000 (UTC) From: Cornelia Huck In-Reply-To: <20230222075157-mutt-send-email-mst@kernel.org> References: <20230217154529.33508-2-parav@nvidia.com> <87wn4byqqb.fsf@redhat.com> <20230221124013-mutt-send-email-mst@kernel.org> <20230221125057-mutt-send-email-mst@kernel.org> <20230221130713-mutt-send-email-mst@kernel.org> <87356yaxaz.fsf@redhat.com> <20230222064936-mutt-send-email-mst@kernel.org> <87wn49aopg.fsf@redhat.com> <20230222075157-mutt-send-email-mst@kernel.org> Date: Wed, 22 Feb 2023 14:26:46 +0100 Message-ID: <87ttzdal0p.fsf@redhat.com> MIME-Version: 1.0 Subject: [virtio-comment] Re: [PATCH v3 1/2] virtio-net: Describe dev cfg fields read only Content-Type: text/plain To: "Michael S. Tsirkin" Cc: Parav Pandit , "virtio-dev@lists.oasis-open.org" , "virtio-comment@lists.oasis-open.org" , Shahaf Shuler List-ID: On Wed, Feb 22 2023, "Michael S. Tsirkin" wrote: > On Wed, Feb 22, 2023 at 01:07:07PM +0100, Cornelia Huck wrote: >> On Wed, Feb 22 2023, "Michael S. Tsirkin" wrote: >> >> > On Wed, Feb 22, 2023 at 10:01:24AM +0100, Cornelia Huck wrote: >> >> On Tue, Feb 21 2023, "Michael S. Tsirkin" wrote: >> >> >> >> > On Tue, Feb 21, 2023 at 05:59:52PM +0000, Parav Pandit wrote: >> >> >> >> >> >> > From: Michael S. Tsirkin >> >> >> > Sent: Tuesday, February 21, 2023 12:52 PM >> >> >> > >> >> >> > On Tue, Feb 21, 2023 at 05:50:09PM +0000, Parav Pandit wrote: >> >> >> > > Hence, it should be mentioned as read-only fields, so when the driver writes >> >> >> > something to read-only fields, it can be considered as undefined behavior on >> >> >> > such fields. >> >> >> > > >> >> >> > >> >> >> > In the description not in the normative statements. normative sections just tell >> >> >> > driver what it must and must not do, in the standard RFC terms. >> >> >> > >> >> >> Got it. >> >> >> I will shift them as read-only in the description section. >> >> >> And normative in the device and driver section. >> >> >> Device section: >> >> >> Any writes to config space fields is ignored by the device, because these are read-only fields for the driver. >> >> > >> >> > writes is plural so "are ignored" >> >> > >> >> > but more importantly use rfc terms in normative sections. >> >> >> >> I don't think you need to talk about "read-only" in the normative >> >> sections (that belongs to the descriptive sections.) I'd use >> >> >> >> "The device MUST ignore any writes to config space fields by the >> >> driver." >> > >> > Hmm. Is this something we previously required for read only fields? >> >> So, better make it SHOULD? >> >> (The only alternative to ignoring I see is breaking the device, and I >> think ignoring is preferable.) > > We can just skip adding a new requirement completely - we'll never get > there with a compliant driver. This is what we do e.g. for MMIO. > Why not? That would be fine with me as well. > This has an advantage as this allows backing config with regular RAM. > Also I feel that since it always said "read only for driver" then > this implies a restriction on driver not the device. Indeed. The normative statement below should be enough to make that "read-only for the driver" thing obvious. > >> > >> > >> >> > >> >> >> >> >> >> Driver section: >> >> >> Driver must not write to read-only fields. >> >> >> >> "The driver MUST NOT write to any config space field." This publicly archived list offers a means to provide input to the OASIS Virtual I/O Device (VIRTIO) TC. In order to verify user consent to the Feedback License terms and to minimize spam in the list archive, subscription is required before posting. Subscribe: virtio-comment-subscribe@lists.oasis-open.org Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org List help: virtio-comment-help@lists.oasis-open.org List archive: https://lists.oasis-open.org/archives/virtio-comment/ Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lists Committee: https://www.oasis-open.org/committees/virtio/ Join OASIS: https://www.oasis-open.org/join/