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 738B79864E3 for ; Thu, 2 Dec 2021 10:27:24 +0000 (UTC) From: Cornelia Huck In-Reply-To: <3298108.H8ur0sk1vH@silver> References: <9053000.DQESySOnJA@silver> <8735ndiwjh.fsf@redhat.com> <3298108.H8ur0sk1vH@silver> Date: Thu, 02 Dec 2021 11:27:17 +0100 Message-ID: <87wnkngv3u.fsf@redhat.com> MIME-Version: 1.0 Subject: Re: [virtio-comment] Re: [PATCH v2 0/2] Add VIRTIO_RING_F_LARGE_INDIRECT_DESC Content-Type: text/plain To: Christian Schoenebeck Cc: virtio-comment@lists.oasis-open.org, Stefan Hajnoczi , Greg Kurz List-ID: On Tue, Nov 30 2021, Christian Schoenebeck wrote: > On Dienstag, 30. November 2021 14:48:50 CET Cornelia Huck wrote: >> On Tue, Nov 30 2021, Christian Schoenebeck wrote: >> > And what about the intended availability of this new virtio_pci_common_cfg >> > field "queue_indirect_size", should it be optional per se, independent of >> > the virtio version or rather a mandatory field in upcoming virtio >> > version? >> We should keep that field depending upon the feature bit IMHO. > > So you are suggesting the existence of "queue_indirect_size" field to be > dependent on feature flag VIRTIO_RING_F_LARGE_INDIRECT_DESC instead of being > dependent on the virtio version. Yes. > Stefan, would that also suit your intended 2nd use case of lowering the max. > descriptor count *below* Queue Size? It would be somewhat different from what > I suggested here in patch 2 [which was min(QueueSize, queue_indirect_size) if > VIRTIO_RING_F_LARGE_INDIRECT_DESC not set], but it could be fine as well. I think that a configurable value for the descriptor count needs to depend on the feature bit as well. > Maybe the name VIRTIO_RING_F_LARGE_INDIRECT_DESC might then a bit misleading > though, because the flag would also be set for forcing small limits. VIRTIO_RING_F_CONFIGURABLE_INDIRECT_DESC ? > > Another issue I just realized: there is also an ambiguity in this v2 what the > maximum descriptor count actually relates to. Should it be > > 1. max. indirect descriptor count per indirect descriptor table > > or > > 2. max. indirect descriptor count per vring slot (i.e. the sum from multiple > indirect descriptor tables within the same message) > > Case 2 applies to QEMU's implementation right now AFAICS. The max. possible > bulk transfer size is lower in case 2 accordingly. 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/