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 0481F9866EB for ; Fri, 18 Mar 2022 16:10:39 +0000 (UTC) From: Cornelia Huck In-Reply-To: <11686863.Z9n2BMzBuM@silver> References: <4735344.EBYxvr1mta@silver> <3040881.qp741xram0@silver> <87cziksm5h.fsf@redhat.com> <11686863.Z9n2BMzBuM@silver> Date: Fri, 18 Mar 2022 17:10:34 +0100 Message-ID: <871qyzs0lh.fsf@redhat.com> MIME-Version: 1.0 Subject: Re: [virtio-comment] Re: [PATCH v3 4/4] Add CCW configuration field "indirect_num" Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable To: Christian Schoenebeck Cc: virtio-comment@lists.oasis-open.org, Stefan Hajnoczi , Greg Kurz , Dominique Martinet , Halil Pasic List-ID: On Fri, Mar 18 2022, Christian Schoenebeck wrote: > On Donnerstag, 17. M=C3=A4rz 2022 15:12:42 CET Cornelia Huck wrote: >> On Wed, Mar 16 2022, Christian Schoenebeck wrot= e: >> > +Since revision 3, \field{indirect_num} exists, which is supposed to >> > reflect the +Queue Indirect Size (i.e. the maximum length of indirect >> > descriptor tables) +supported by device for this queue. >>=20 >> It still depends on the feature flag, though. >>=20 >> Maybe >>=20 >> "If revision 2 or lower is set, struct vq_config_block extends up to >> \field{max_num}. >>=20 >> If revision 3 or higher is set, struct vq_config_block extends to >> \field{max_indirect_num}. If VIRTIO_RING_F_INDIRECT_SIZE is negotiated, >> \field{indirect_max_num} contains the maximum Queue Indirect Size >> (i.e. the maximum length of indirect descriptor tables) supported by the >> device for this queue; otherwise, its contents are unpredictable." > > Maybe rather something like this instead: > > "Actual size of struct vq_config_block depends on the virtio-ccw revision= . > > If revision 2 or lower is set, struct vq_config_block extends up to > *including* \field{max_num}. > > If revision 3 or higher is set, struct vq_config_block extends up to > *including* \field{max_indirect_num}. If VIRTIO_RING_F_INDIRECT_SIZE is= =20 > negotiated, \field{indirect_max_num} contains the maximum Queue Indirect = Size > (i.e. the maximum length of indirect descriptor tables) supported by the > device for this queue; otherwise, its contents are *undefined*." Hm, I was coming from the driver's perspective here. But "undefined" probably captures "junk in there, do not use" better. Ack on your other points. >> We should include a device normative statement: >>=20 >> "The device MUST NOT offer VIRTIO_RING_F_INDIRECT_SIZE, unless at least >> revision 3 is set, and therefore \field{max_indirect_num} respectively >> \field{indirect_num} are available." > > Oh, you are suggesting two different names for those two fields?=20 > "max_indirect_num" vs. "indirect_num". If yes, why? The "max_indirect_num" goes with the "max_num": this is the maximum value that the device supports (the "maximum maximum", in a way :). "indirect_num" is the actual upper limit while the device is in use. > > Otherwise about adding that normative statement in general here: sure, ma= kes=20 > sense. 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/