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 3FCEA986499 for ; Wed, 12 Jan 2022 17:21:01 +0000 (UTC) From: Cornelia Huck References: Date: Wed, 12 Jan 2022 18:20:53 +0100 Message-ID: <87lezkx43u.fsf@redhat.com> MIME-Version: 1.0 Subject: [virtio-comment] [oasis-tcs/virtio-spec] Device specific Feature bits numbering is not aligned (Issue #131) Content-Type: text/plain To: Max Gurtovoy Cc: virtio-dev@lists.oasis-open.org, virtio-comment@lists.oasis-open.org List-ID: > Feature bits 56 to 63 are taken by the virtio-net device and not reflected in the generic feature bits accounting. Thank you for reporting this, forwarding to the lists for discussion. It seems like we're in a bit of a pickle: The spec says that the higher feature bits are reserved for future generic extensions, but virtio-net is already using some bits in that space (as they have already exhausted the lower device-specific bits). Now we cannot undo the already reserved bits, but obviously we need space both for generic extensions and device-specific extensions. Fortunately, we're not short on feature bits, we can simply consider the bits beyond 63. I'd like to propose the following: - bits 41-49: reserved for future extensions - bits 50-63: used for specific device types - bits 64-127: used for specific device types - bits 128 and above: reserved for future extensions This gives us room for both generic and device-specific extensions in the first 64 bits for some more time before we have to go to bit 64 and beyond. Thoughts? We need to figure that out before the 1.2 release. 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/