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 44D2B986553 for ; Wed, 8 Dec 2021 15:28:31 +0000 (UTC) From: Cornelia Huck In-Reply-To: References: <87fsr4thvo.fsf@redhat.com> <10245090.BqRs5aQnp2@silver> Date: Wed, 08 Dec 2021 16:28:07 +0100 Message-ID: <877dcft8u0.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: Stefan Hajnoczi , Christian Schoenebeck Cc: virtio-comment@lists.oasis-open.org, Greg Kurz List-ID: On Wed, Dec 08 2021, Stefan Hajnoczi wrote: > On Wed, Dec 08, 2021 at 01:26:54PM +0100, Christian Schoenebeck wrote: >> One more thought: what about making the new 'queue_indirect_size' config field >> 32 bit wide instead of 16 bit? That would easily mitigate the issue of the >> aggregated limit discussed here, and would in general be more future safe, >> i.e. considering that there might be either nested/multi-level indirect >> descriptor tables or chained tables in future? The cost would be low, right? > > The MMIO transport has 32-bit fields, so there doesn't seem to be a > strict requirement to use 16 bits for descriptor counts. > > I think you're right that the cost is low. Usually it's the access > itself that carries a cost (a VM exit or bus transaction) and 2 vs 4 > byte transfers don't really matter. For ccw, I think we'd simply include the value in a control block, and it does not really matter whether that control block is 2 bytes longer. So, no objection from me. 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/