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 754D0C77B75 for ; Mon, 15 May 2023 05:12:21 +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 A13371922EB for ; Mon, 15 May 2023 05:12:20 +0000 (UTC) Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id 80E499864EE for ; Mon, 15 May 2023 05:12:20 +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 69F3B986348; Mon, 15 May 2023 05:12:20 +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 581DF98635A for ; Mon, 15 May 2023 05:12:20 +0000 (UTC) X-Virus-Scanned: amavisd-new at kavi.com X-MC-Unique: OhSvla4UMD-nq79DFgnepQ-1 X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1684127537; x=1686719537; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=tqGYSucWjH3m/t7zcN76j7dLHnGioTQTJUoB1Po7lQY=; b=IODmTgpwUOkjB+76L/6Vnmk6RaW3M5Wqtu10mY7QV+dV6U89SCMVyegZR6edTgdyL/ rmYoNDEIMTJ9iYuW4YTul/TYJoqpAGMalMxVCblMEpwLSK1qeAgIaVDsplrtGyZdQQvL 1qauJneHWdUu864YhDHPYWBT0g2ro+RrEqoOAymIL5crs3QK3E3p8TqLIrEakJpXmL3E +oVm3YwQaY1Z5gII1hdAGYk/4yXqn9Yz4BrlFnO8SSrVZB+CDNVm6NcLregiFoyShVwg sU1d4/F4V4mbXD1MV/tpZCYcSocDX8yrUhVzYBXidPao9BFyF44KYWqhnbC9bKBIIJmH RXsw== X-Gm-Message-State: AC+VfDzx99z4DGrE5GVNJBu45JtQoYm2laTRdvvqaQkq80FEDp60HXug ix85ZtDdkZ5jmQX6W/7mlFA2lXScwxghwv7dyq989Nmafchn6WuNz1QyP+6oBpaxnOShMO+4u1q N60Abhnk8PJPdq5nZlXsGJ6wlNhG9 X-Received: by 2002:a17:90a:d988:b0:24e:20d9:4e5b with SMTP id d8-20020a17090ad98800b0024e20d94e5bmr34501297pjv.9.1684127537500; Sun, 14 May 2023 22:12:17 -0700 (PDT) X-Google-Smtp-Source: ACHHUZ6qiWwZ2eTdruCX+TtQucljuNRqxrEvruGe/IF/kg/QGthMYiyxOXrK6EunEb0gisFwfIRaJg== X-Received: by 2002:a17:90a:d988:b0:24e:20d9:4e5b with SMTP id d8-20020a17090ad98800b0024e20d94e5bmr34501284pjv.9.1684127537230; Sun, 14 May 2023 22:12:17 -0700 (PDT) Message-ID: Date: Mon, 15 May 2023 13:12:12 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 To: Parav Pandit Cc: "Michael S. Tsirkin" , "virtio-dev@lists.oasis-open.org" , "cohuck@redhat.com" , "david.edmondson@oracle.com" , "sburla@marvell.com" , Yishai Hadas , Maor Gottlieb , "virtio-comment@lists.oasis-open.org" , Shahaf Shuler References: <20230506000135.628899-1-parav@nvidia.com> <20230507093959-mutt-send-email-mst@kernel.org> From: Jason Wang In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Subject: [virtio-dev] Re: [virtio-comment] RE: [PATCH v2 0/2] transport-pci: Introduce legacy registers access using AQ 在 2023/5/11 22:31, Parav Pandit 写道: >> From: Jason Wang >> Sent: Thursday, May 11, 2023 3:17 AM >>> a configq/cmdq discussion is for new features for PF, VF, and SF/SIOV >>> devices to work in _non_ backward compatible way, because for new >>> features there is no such thing as backward compatibility between >>> guest driver and the device. >> Ok, so what command did configq/cmdq have? >> I thought it was similar to transport virtqueue, but it looks more like a control virtqueue here. > Yes, it is more like a cvq to do device attributes discovery and configuration. > Just that its generic enough. > For example > creating VQ that spans multiple physical addresses. > Discovery and enabling new device attributes which are rarely accessed or accessed during device init/cleanup time. > > The fundamental difference between cfgvq to tvq is: > Cfgvq is between the member virtio device and its driver. > Tvq=aq is on group owner of the virtio device. > >>>>> Compatibility is coming at a cost which is not scaling. >>>>> If you attempt to scale, it breaks the future path forward to go without >> mediation. >>>>>>> So eve growing these fields and optionally placement on configq >>>>>>> doesn't really help and device builder to build it efficiently >>>>>>> (without much predictability). >>>>>> Config queue is not the only choice, we have a lot of other >>>>>> choices (for example PASID may help to reduce the on-chip resources). >>>>>> >>>>> PASID is for process isolation security construct, it is not for transportation. >>>> I meant with PASID you don't even need a BAR. >>>> >>> Not sure I fully understand, but my guess is, this is coming from >>> mediation thought process. >> Not actually. I meant, for example without PASID, for modern devices, the >> common cfg structure must be placed on a BAR through MMIO. >> >> But with the help of PASID, it could stay in the memory and the device can fetch >> it via DMA. The help to reduce the resources for registers. >> > Yes, it can stay in memory and device can fetch via DMA using a VQ using its own q from guest driver. > Why does it need PASID? Let me clarify my understanding. If we want a per VF virtqueue that is used by the hypervisor. We need PASID. Otherwise not. Thanks --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org