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=-15.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,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 392CEC433DB for ; Wed, 10 Feb 2021 05:56:33 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 5153960233 for ; Wed, 10 Feb 2021 05:56:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5153960233 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:56868 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l9iUJ-0005U0-1r for qemu-devel@archiver.kernel.org; Wed, 10 Feb 2021 00:56:31 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:41024) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l9iSy-000532-JL for qemu-devel@nongnu.org; Wed, 10 Feb 2021 00:55:08 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:44317) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l9iSw-00047B-6o for qemu-devel@nongnu.org; Wed, 10 Feb 2021 00:55:08 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612936505; 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=Je5p7aN/jqBrz0XrAj1lI4ldSNVdB/VBKt3tWiHiYvw=; b=ZxcohGrNIqmm8mwHo+v/gfgSVVYPrJrGDRyB8loprRtx51RQ+ft4mZSZTKqKcPwGljVFts yidkeuz5y8wqmGwxEAfbjaN4/boXNKI6HJhgXVPxIIeqcxrbYizFYS3xNUWtnXAaGlODfM J5/jVgB0MCvjY1gemugOsghpkZXl0Ng= 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-41-o-gX3yZhOjyEE_crabprfQ-1; Wed, 10 Feb 2021 00:55:03 -0500 X-MC-Unique: o-gX3yZhOjyEE_crabprfQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 03AAF10066EF; Wed, 10 Feb 2021 05:55:02 +0000 (UTC) Received: from [10.72.12.223] (ovpn-12-223.pek2.redhat.com [10.72.12.223]) by smtp.corp.redhat.com (Postfix) with ESMTP id 186F457; Wed, 10 Feb 2021 05:54:50 +0000 (UTC) Subject: Re: [RFC 05/10] vhost: Add vhost_dev_from_virtio To: Eugenio Perez Martin References: <20210129205415.876290-1-eperezma@redhat.com> <20210129205415.876290-6-eperezma@redhat.com> <569ace3d-f2c3-8b9f-63f5-809ce7067046@redhat.com> From: Jason Wang Message-ID: <7ddc8982-b422-beec-8812-60706105fb72@redhat.com> Date: Wed, 10 Feb 2021 13:54:48 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jasowang@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Received-SPF: pass client-ip=216.205.24.124; envelope-from=jasowang@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.57, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.265, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Parav Pandit , Juan Quintela , "Michael S. Tsirkin" , qemu-level , Markus Armbruster , Stefano Garzarella , Harpreet Singh Anand , Xiao W Wang , Stefan Hajnoczi , Eli Cohen , virtualization@lists.linux-foundation.org, Michael Lilja , Jim Harford , Rob Miller Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2021/2/9 下午11:35, Eugenio Perez Martin wrote: > On Fri, Feb 5, 2021 at 4:52 AM Jason Wang wrote: >> >> On 2021/2/4 下午5:25, Eugenio Perez Martin wrote: >>> On Thu, Feb 4, 2021 at 4:14 AM Jason Wang wrote: >>>> On 2021/2/2 下午6:17, Eugenio Perez Martin wrote: >>>>> On Tue, Feb 2, 2021 at 4:31 AM Jason Wang wrote: >>>>>> On 2021/2/1 下午4:28, Eugenio Perez Martin wrote: >>>>>>> On Mon, Feb 1, 2021 at 7:13 AM Jason Wang wrote: >>>>>>>> On 2021/1/30 上午4:54, Eugenio Pérez wrote: >>>>>>>>> Signed-off-by: Eugenio Pérez >>>>>>>>> --- >>>>>>>>> include/hw/virtio/vhost.h | 1 + >>>>>>>>> hw/virtio/vhost.c | 17 +++++++++++++++++ >>>>>>>>> 2 files changed, 18 insertions(+) >>>>>>>>> >>>>>>>>> diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h >>>>>>>>> index 4a8bc75415..fca076e3f0 100644 >>>>>>>>> --- a/include/hw/virtio/vhost.h >>>>>>>>> +++ b/include/hw/virtio/vhost.h >>>>>>>>> @@ -123,6 +123,7 @@ uint64_t vhost_get_features(struct vhost_dev *hdev, const int *feature_bits, >>>>>>>>> void vhost_ack_features(struct vhost_dev *hdev, const int *feature_bits, >>>>>>>>> uint64_t features); >>>>>>>>> bool vhost_has_free_slot(void); >>>>>>>>> +struct vhost_dev *vhost_dev_from_virtio(const VirtIODevice *vdev); >>>>>>>>> >>>>>>>>> int vhost_net_set_backend(struct vhost_dev *hdev, >>>>>>>>> struct vhost_vring_file *file); >>>>>>>>> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c >>>>>>>>> index 28c7d78172..8683d507f5 100644 >>>>>>>>> --- a/hw/virtio/vhost.c >>>>>>>>> +++ b/hw/virtio/vhost.c >>>>>>>>> @@ -61,6 +61,23 @@ bool vhost_has_free_slot(void) >>>>>>>>> return slots_limit > used_memslots; >>>>>>>>> } >>>>>>>>> >>>>>>>>> +/* >>>>>>>>> + * Get the vhost device associated to a VirtIO device. >>>>>>>>> + */ >>>>>>>>> +struct vhost_dev *vhost_dev_from_virtio(const VirtIODevice *vdev) >>>>>>>>> +{ >>>>>>>>> + struct vhost_dev *hdev; >>>>>>>>> + >>>>>>>>> + QLIST_FOREACH(hdev, &vhost_devices, entry) { >>>>>>>>> + if (hdev->vdev == vdev) { >>>>>>>>> + return hdev; >>>>>>>>> + } >>>>>>>>> + } >>>>>>>>> + >>>>>>>>> + assert(hdev); >>>>>>>>> + return NULL; >>>>>>>>> +} >>>>>>>> I'm not sure this can work in the case of multiqueue. E.g vhost-net >>>>>>>> multiqueue is a N:1 mapping between vhost devics and virtio devices. >>>>>>>> >>>>>>>> Thanks >>>>>>>> >>>>>>> Right. We could add an "vdev vq index" parameter to the function in >>>>>>> this case, but I guess the most reliable way to do this is to add a >>>>>>> vhost_opaque value to VirtQueue, as Stefan proposed in previous RFC. >>>>>> So the question still, it looks like it's easier to hide the shadow >>>>>> virtqueue stuffs at vhost layer instead of expose them to virtio layer: >>>>>> >>>>>> 1) vhost protocol is stable ABI >>>>>> 2) no need to deal with virtio stuffs which is more complex than vhost >>>>>> >>>>>> Or are there any advantages if we do it at virtio layer? >>>>>> >>>>> As far as I can tell, we will need the virtio layer the moment we >>>>> start copying/translating buffers. >>>>> >>>>> In this series, the virtio dependency can be reduced if qemu does not >>>>> check the used ring _F_NO_NOTIFY flag before writing to irqfd. It >>>>> would enable packed queues and IOMMU immediately, and I think the cost >>>>> should not be so high. In the previous RFC this check was deleted >>>>> later anyway, so I think it was a bad idea to include it from the start. >>>> I am not sure I understand here. For vhost, we can still do anything we >>>> want, e.g accessing guest memory etc. Any blocker that prevent us from >>>> copying/translating buffers? (Note that qemu will propagate memory >>>> mappings to vhost). >>>> >>> There is nothing that forbids us to access directly, but if we don't >>> reuse the virtio layer functionality we would have to duplicate every >>> access function. "Need" was a too strong word maybe :). >>> >>> In other words: for the shadow vq vring exposed for the device, qemu >>> treats it as a driver, and this functionality needs to be added to >>> qemu. But for accessing the guest's one do not reuse virtio.c would be >>> a bad idea in my opinion. >> >> The problem is, virtio.c is not a library and it has a lot of dependency >> with other qemu modules basically makes it impossible to be reused at >> vhost level. >> > While virtio.c as a whole has dependencies, I think that the functions > needed in the original RFC do not have these dependencies. > > However I see how to split vring dataplane from virtio device > management can benefit. If you can split them out, that would be fine. > >> We can solve this by: >> >> 1) split the core functions out as a library or >> 2) switch to use contrib/lib-vhostuser but needs to decouple UNIX socket >> transport >> >> None of the above looks trivial and they are only device codes. For >> shadow virtqueue, we need driver codes as well where no code can be reused. >> >> As we discussed, we probably need IOVA allocated when forwarding >> descriptors between the two virtqueues. So my feeling is we can have our >> own codes to start then we can consider whether we can reuse some from >> the existing virtio.c or lib-vhostuser. >> > As I see it, if we develop our own code a lot of it will be copied > from current virtio.c, which itself duplicates a lot of contrib/ lib > functionality. > > Maybe it's better to combine your proposals and decouple the vring > functions, the vhost transport, and the qemu virtio device management, > so other projects can reuse them directly? I think this can work. > > I still think this can be left for a later series with buffer > forwarding on top of this one, do you think they can/should be merged > independently? Since you post a new series, let's see. Thanks > > Thanks! > >> Thanks >> >> >>>> Thanks >>>> >>>> >>>>> >>>>> >>>>> >>>>>> Thanks >>>>>> >>>>>> >>>>>>> I need to take this into account in qmp_x_vhost_enable_shadow_vq too. >>>>>>> >>>>>>>>> + >>>>>>>>> static void vhost_dev_sync_region(struct vhost_dev *dev, >>>>>>>>> MemoryRegionSection *section, >>>>>>>>> uint64_t mfirst, uint64_t mlast,