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 C3979C7619A for ; Wed, 12 Apr 2023 04:54:07 +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 0B1FB42B67 for ; Wed, 12 Apr 2023 04:54:07 +0000 (UTC) Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id ECEC4986512 for ; Wed, 12 Apr 2023 04:54:06 +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 E0DDC9841AB; Wed, 12 Apr 2023 04:54:06 +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 D091C986509 for ; Wed, 12 Apr 2023 04:54:06 +0000 (UTC) X-Virus-Scanned: amavisd-new at kavi.com X-MC-Unique: RhO7CmMxNDuysDUoHKbWaw-1 X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1681275244; x=1683867244; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=qFgqrtqus2IpUXl0nutVva0zyE3uzrGxSSg+fJrzG80=; b=Zosiy4tqfd8/DnNAxmLCws+2OKn2t8bE7X8JtFqO0Y/TYmAIHHrg6xNspWMXL8qd3n G3uF4OFKLSI1Cbv60VUdgZjI95HDKKNXfu2jzAlT8Jr+nvvxOB83FyHoDVvyNCZ71Zpn GoR75iZiIYaS1dr9BrKR6VmYjCL7S8dj0hZvdbG/FbG/Ic7JP+I1y+HI4K2WzEQZRFBU 8XfqNOEoD2APupDXKkSPFzlZ70qOev7/Gxjw7gj700jSd4grQltQP8ukXhK+/TOn4Dum s0/HF4i/bqnALxZrQLwb1XQ1uU1L8BJLK0Gb2ZRr3FmDmrjicpmUznohAserwnjImFxO AIAw== X-Gm-Message-State: AAQBX9f0fPS8YrN/2Lwj5V8y+iBkiADM4LP5jNPwCG3nPu0sLkTsVmGJ nRWxJqHex5/FPni6zXjr/Nj4SjIseE6Oxerdu3mRSfU3AhBsUXK/rw4nj4vNqkF6ukcR7IbBTXW E/P87DxkBrcgX9gE1BETrMTKHmk7q0IrK/VpBgjS7bjiLPCSyZEEV3BPu6A== X-Received: by 2002:a05:620a:29cb:b0:74a:508:e788 with SMTP id s11-20020a05620a29cb00b0074a0508e788mr4415103qkp.8.1681275244036; Tue, 11 Apr 2023 21:54:04 -0700 (PDT) X-Google-Smtp-Source: AKy350Yuy+KVIbrLNmMuRXk7vz1n4r8ngkr4j3yOCiXUBoSSwpjPPWx3Wo7YjZuoxzKMtCggHLSxYzU232cnOVIQP90= X-Received: by 2002:a05:620a:29cb:b0:74a:508:e788 with SMTP id s11-20020a05620a29cb00b0074a0508e788mr4415094qkp.8.1681275243774; Tue, 11 Apr 2023 21:54:03 -0700 (PDT) MIME-Version: 1.0 References: <20230330225834.506969-1-parav@nvidia.com> <20230330225834.506969-9-parav@nvidia.com> <307a9f8f-6184-0403-97ab-1b1c16d4fd3c@nvidia.com> <20230411172207-mutt-send-email-mst@kernel.org> <20230412001803-mutt-send-email-mst@kernel.org> In-Reply-To: <20230412001803-mutt-send-email-mst@kernel.org> From: Jason Wang Date: Wed, 12 Apr 2023 12:53:52 +0800 Message-ID: To: "Michael S. Tsirkin" Cc: Parav Pandit , "virtio-dev@lists.oasis-open.org" , "cohuck@redhat.com" , "virtio-comment@lists.oasis-open.org" , Shahaf Shuler , Satananda Burla X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Subject: [virtio-dev] Re: [virtio-comment] Re: [virtio-dev] [PATCH 08/11] transport-pci: Introduce virtio extended capability On Wed, Apr 12, 2023 at 12:20=E2=80=AFPM Michael S. Tsirkin wrote: > > On Wed, Apr 12, 2023 at 12:07:26PM +0800, Jason Wang wrote: > > On Wed, Apr 12, 2023 at 5:25=E2=80=AFAM Michael S. Tsirkin wrote: > > > > > > On Tue, Apr 11, 2023 at 07:01:16PM +0000, 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 the= m in > > > > > > extended capability, it will not work. > > > > > > > > > > > > > > > > It is kind of intended since it is only used for new PCI-E featur= es: > > > > > > > > > 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? > > > > > > > > > " > > > > > +The location of the virtio structures that depend on the PCI Exp= ress > > > > > +capability are specified using a vendor-specific extended capabi= lities > > > > > +on the extended capabilities list in PCI Express extended config= uration > > > > > +space of the device. > > > > > " > > > > > > > > > > > To make it backward compatible, a device needs to expose existi= ng > > > > > > structure in legacy area. And extended structure for same capab= ility > > > > > > 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. > > > > New fields don=E2=80=99t need to be placed in PCI cap, because no d= river is looking there. > > > > > > > > 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 capabi= lity. Michael > > > > > suggest to add a new feature, but the driver may not negotiate th= e feature > > > > > which requires more thought. > > > > > > > > > Not sure I understand feature bit. > > > > > > This is because we have a concept of dependency between > > > features but not a concept of dependency of feature on > > > capability. > > > > > > > PCI transport fields existence is usually not dependent on upper la= yer protocol. > > > > > > > > > > We may need it even sooner than this because the AQ patch is ex= panding > > > > > > 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=E2=80=99t need cap extension. > > > > > > > > > > > > You know, thinking about this, I begin to feel that we should > > > require that if at least one extended config exists then > > > all caps present in the regular config are *also* > > > mirrored in the extended config. IOW extended >=3D regular. > > > The reason is that extended config can be emulated more efficiently > > > (2x less exits). > > > > Any reason for it to get less exits? > > For a variety of reasons having to do with buggy hardware e.g. linux > likes to use cf8/cfc for legacy ranges. 2 accesses are required for each > read/write. extended space is just 1. > Ok. > > > At least it has not been done in > > current Qemu's emulation. (And do we really care about the performance > > of config space access?) > > > > Thanks > > For boot speed, yes. Not minor 5% things but 2x, sure. If we care about boot speed we should avoid using the PCI layer in the guest completely. Thanks > > > > WDYT? > > > > > > > > > -- > > > MST > > > > > > 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-l= ists > Committee: https://www.oasis-open.org/committees/virtio/ > Join OASIS: https://www.oasis-open.org/join/ > --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org