From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from ws5-mx01.kavi.com (ws5-mx01.kavi.com [34.193.7.191]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 37A74C77B6E for ; Wed, 12 Apr 2023 04:21:09 +0000 (UTC) Received: from lists.oasis-open.org (oasis.ws5.connectedcommunity.org [10.110.1.242]) by ws5-mx01.kavi.com (Postfix) with ESMTP id A7DB22AC59 for ; Wed, 12 Apr 2023 04:21:08 +0000 (UTC) Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id 9F7F99865A6 for ; Wed, 12 Apr 2023 04:21:08 +0000 (UTC) Received: from host09.ws5.connectedcommunity.org (host09.ws5.connectedcommunity.org [10.110.1.97]) by lists.oasis-open.org (Postfix) with QMQP id 934909864B3; Wed, 12 Apr 2023 04:21:08 +0000 (UTC) Mailing-List: contact virtio-dev-help@lists.oasis-open.org; run by ezmlm List-ID: Sender: Precedence: bulk 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 844CA986509 for ; Wed, 12 Apr 2023 04:21:08 +0000 (UTC) X-Virus-Scanned: amavisd-new at kavi.com X-MC-Unique: F7E5TSSNNFmNYbWN60uKaw-1 X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1681273263; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=PqpuHF4Mi9VcxFgkf1M9251n7aY1Xeds05xh7jpHVDk=; b=t2VexRgbctXng/QH72eMfM5xkF8V0Ef/3HyXMM0DAFItHZGGq0LWUIu9reFvh/Ap3t NMAXiVc3V8Fvzt13QdK6s3psdt83el3mmurHOYHjzSy6mURBSC/UsyXHX/ftYVPfn74U MoCaLvWrwDTBVKFiA99YKdKxCj16zjygAIHaqDoTCIMnm0OTJj2FOFv/GaYL8aGuJvHF NXN+pgc53s2uKoBQEhS7JE3/npi23pLmLFHi7DbaaiWhKy0piVfKNjyHVQp85tMiEGzj /eqOmdPgXgXfTpoBhO7t7ODo73INp98htCPM/MMUsi1aC2CJQ22/XxZPD8MX7+uR5NT1 Rbcg== X-Gm-Message-State: AAQBX9f+wr3k+mnBF39U8OsXSOxgycME0icZCP1E+lWAS5g1HLIxr9L+ Bmq5LjqVFq1vMp5GL8NywqzMYLw54AYnJvhdsXiLS/21blxw3ojZtBOozRUohd9/1kGMwbNAJ2J afh15UIOIDPIJnaymTRV0VHIkEpDt X-Received: by 2002:a1c:7406:0:b0:3f0:7db5:6077 with SMTP id p6-20020a1c7406000000b003f07db56077mr717643wmc.39.1681273263016; Tue, 11 Apr 2023 21:21:03 -0700 (PDT) X-Google-Smtp-Source: AKy350YxP9aJXz8zaC1mmG3g9Huuh5f0i4O6Rkm8eciBOAClCMWfphsnda4MjtMqfX1hDsDi2uIhDQ== X-Received: by 2002:a1c:7406:0:b0:3f0:7db5:6077 with SMTP id p6-20020a1c7406000000b003f07db56077mr717632wmc.39.1681273262744; Tue, 11 Apr 2023 21:21:02 -0700 (PDT) Date: Wed, 12 Apr 2023 00:20:59 -0400 From: "Michael S. Tsirkin" To: Jason Wang Cc: Parav Pandit , "virtio-dev@lists.oasis-open.org" , "cohuck@redhat.com" , "virtio-comment@lists.oasis-open.org" , Shahaf Shuler , Satananda Burla Message-ID: <20230412002017-mutt-send-email-mst@kernel.org> References: <20230330225834.506969-1-parav@nvidia.com> <20230330225834.506969-9-parav@nvidia.com> <307a9f8f-6184-0403-97ab-1b1c16d4fd3c@nvidia.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Subject: Re: [virtio-dev] [PATCH 08/11] transport-pci: Introduce virtio extended capability On Wed, Apr 12, 2023 at 12:04:45PM +0800, Jason Wang wrote: > On Wed, Apr 12, 2023 at 3:01 AM Parav Pandit wrote: > > > > > > > From: virtio-dev@lists.oasis-open.org On > > > Behalf Of Jason Wang > > > Sent: Monday, April 10, 2023 11:29 PM > > > > > > However, it is not backward compatible, if the device place them in > > > > extended capability, it will not work. > > > > > > > > > > It is kind of intended since it is only used for new PCI-E features: > > > > > New fields in new extended pci cap area is fine. > > Migrating old fields to be present in the new extended pci cap, is not your intention. Right? > > Right, but what I want to say is, such migration may cause unnecessary > problems. And I don't see why it is a must for your legacy MMIO bar > proposal. > > > > > > " > > > +The location of the virtio structures that depend on the PCI Express > > > +capability are specified using a vendor-specific extended capabilities > > > +on the extended capabilities list in PCI Express extended configuration > > > +space of the device. > > > " > > > > > > > To make it backward compatible, a device needs to expose existing > > > > structure in legacy area. And extended structure for same capability > > > > in extended pci capability region. > > > > > > > > In other words, it will have to be a both places. > > > > > > Then we will run out of config space again? > > No. > > Only currently defined caps to be placed in two places. > > What's the advantage of doing this? > > New drivers should provide backward compatibility so they must scan the pci cap. No, they can start with express cap. Finding one they can skip the old cap completely. > The Old driver can only scan the pci cap. > > > New fields don’t need to be placed in PCI cap, because no driver is looking there. > > It would be much more simple if we forbid placing new fields in the > PCI cap, it is already out of space. > > Thanks > > > > > We probably already discussed this in previous email by now. > > > > > Otherwise we need to deal with the > > > case when existing structures were only placed at extended capability. Michael > > > suggest to add a new feature, but the driver may not negotiate the feature > > > which requires more thought. > > > > > Not sure I understand feature bit. > > PCI transport fields existence is usually not dependent on upper layer protocol. > > > > > > We may need it even sooner than this because the AQ patch is expanding > > > > the structure located in legacy area. > > > > > > Just to make sure I understand this, assuming we have adminq, any reason a > > > dedicated pcie ext cap is required? > > > > > No. it was my short sight. I responded right after above text that AQ doesn’t need cap extension. --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org