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 X-Spam-Level: X-Spam-Status: No, score=-5.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A1744C352A3 for ; Thu, 13 Feb 2020 03:38:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7336D206D7 for ; Thu, 13 Feb 2020 03:38:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="QXMLkkmT" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729617AbgBMDiv (ORCPT ); Wed, 12 Feb 2020 22:38:51 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:28429 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729432AbgBMDiv (ORCPT ); Wed, 12 Feb 2020 22:38:51 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1581565130; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=siHjLti79eNab49m9VmN2I96BJq+1gJqUI5rNubl/tg=; b=QXMLkkmTpluEPqLBmhgyHDw1HO+qR4UMvxEMKn17ZVwpfpofiBbR45nx9/AX3rwkFht03F oKRqVTT7AwDyCDp+4WTAULRgmaxz5DcahVAFlPu39nx3qhhQCa9DX4hf+jVTHX65MdxXIV NaSTNtLXjuEnF33mlg5NeqIlnc8T9wI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-66-nexhK39lNd67jEn2kgmk0g-1; Wed, 12 Feb 2020 22:38:42 -0500 X-MC-Unique: nexhK39lNd67jEn2kgmk0g-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7754713E5; Thu, 13 Feb 2020 03:38:41 +0000 (UTC) Received: from [10.72.13.212] (ovpn-13-212.pek2.redhat.com [10.72.13.212]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9D51C5C101; Thu, 13 Feb 2020 03:38:32 +0000 (UTC) Subject: Re: [PATCH v2 1/5] virtio-mmio: add notify feature for per-queue To: "Michael S. Tsirkin" Cc: virtio-dev@lists.oasis-open.org, Zha Bin , slp@redhat.com, jing2.liu@linux.intel.com, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, chao.p.peng@linux.intel.com, gerry@linux.alibaba.com References: <8a4ea95d6d77a2814aaf6897b5517353289a098e.1581305609.git.zhabin@linux.alibaba.com> <20200211062205-mutt-send-email-mst@kernel.org> <20200212024158-mutt-send-email-mst@kernel.org> <82d99b35-0c64-2eb2-9c23-7af2597b880b@redhat.com> <20200212045245-mutt-send-email-mst@kernel.org> From: Jason Wang Message-ID: Date: Thu, 13 Feb 2020 11:38:31 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20200212045245-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/2/12 =E4=B8=8B=E5=8D=885:55, Michael S. Tsirkin wrote: > On Wed, Feb 12, 2020 at 05:33:06PM +0800, Jason Wang wrote: >> On 2020/2/12 =E4=B8=8B=E5=8D=884:53, Jason Wang wrote: >>> On 2020/2/12 =E4=B8=8B=E5=8D=884:18, Michael S. Tsirkin wrote: >>>> On Wed, Feb 12, 2020 at 11:39:54AM +0800, Jason Wang wrote: >>>>> On 2020/2/11 =E4=B8=8B=E5=8D=887:33, Michael S. Tsirkin wrote: >>>>>> On Mon, Feb 10, 2020 at 05:05:17PM +0800, Zha Bin wrote: >>>>>>> From: Liu Jiang >>>>>>> >>>>>>> The standard virtio-mmio devices use notification register to sig= nal >>>>>>> backend. This will cause vmexits and slow down the >>>>>>> performance when we >>>>>>> passthrough the virtio-mmio devices to guest virtual machines. >>>>>>> We proposed to update virtio over MMIO spec to add the per-queue >>>>>>> notify feature VIRTIO_F_MMIO_NOTIFICATION[1]. It can allow the VM= M to >>>>>>> configure notify location for each queue. >>>>>>> >>>>>>> [1]https://lkml.org/lkml/2020/1/21/31 >>>>>>> >>>>>>> Signed-off-by: Liu Jiang >>>>>>> Co-developed-by: Zha Bin >>>>>>> Signed-off-by: Zha Bin >>>>>>> Co-developed-by: Jing Liu >>>>>>> Signed-off-by: Jing Liu >>>>>>> Co-developed-by: Chao Peng >>>>>>> Signed-off-by: Chao Peng >>>>>> Hmm. Any way to make this static so we don't need >>>>>> base and multiplier? >>>>> E.g page per vq? >>>>> >>>>> Thanks >>>> Problem is, is page size well defined enough? >>>> Are there cases where guest and host page sizes differ? >>>> I suspect there might be. >>> >>> Right, so it looks better to keep base and multiplier, e.g for vDPA. >>> >>> >>>> But I also think this whole patch is unproven. Is someone actually >>>> working on QEMU code to support pass-trough of virtio-pci >>>> as virtio-mmio for nested guests? What's the performance >>>> gain like? >>> >>> I don't know. >>> >>> Thanks >> >> Btw, I think there's no need for a nested environment to test. Current >> eventfd hook to MSIX should still work for MMIO. >> >> Thanks > > Oh yes it's the wildcard thingy but how much extra performance does one= get > from it with MMIO? A couple % might not be worth the trouble for MMIO. The cover letter have some numbers but I'm not sure whether or not it=20 was measured by vhost or other which needs some clarification. Thanks >