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=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 8799EC56202 for ; Wed, 25 Nov 2020 12:14:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1C093206E5 for ; Wed, 25 Nov 2020 12:14:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="MqJjbPP/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728887AbgKYMOq (ORCPT ); Wed, 25 Nov 2020 07:14:46 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:56210 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728077AbgKYMOp (ORCPT ); Wed, 25 Nov 2020 07:14:45 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1606306483; 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=DMmA4XTQ00FJZ1hDsKzyU42iqLETf4QTiXbtu9A5zJg=; b=MqJjbPP/C6o9qfucuBuqx2CznwMGo+pyaMJ6MfWyuY63j8Fy/0De6bfAPZW8rYvM2FSFmv 7Wb8D1esnb3YZCgeOaKRXxSz4QiPRMnH/CyQG/jGke6aiUcJI/bPY4DqKvHXqf0FL7hT4G 36X17Xgzd660EmuUuHiVotQ4HBN3nqg= Received: from mail-qv1-f72.google.com (mail-qv1-f72.google.com [209.85.219.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-456-mZbj6-TYMHiUS3XaL2uDgw-1; Wed, 25 Nov 2020 07:14:42 -0500 X-MC-Unique: mZbj6-TYMHiUS3XaL2uDgw-1 Received: by mail-qv1-f72.google.com with SMTP id y8so2249719qvu.22 for ; Wed, 25 Nov 2020 04:14:42 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=DMmA4XTQ00FJZ1hDsKzyU42iqLETf4QTiXbtu9A5zJg=; b=WlD4a+IbVWVvBqYwHabuhLaTl3k9GxVmZj/mdWuC2dBrD0ExSnFvy8GnurzOHtYHax XEkgRDiefE8qUnrYbF5MZ34hqAbRHLvR0ySvvBO0nHaUkPCHooL8gVj/cYNjerAxZ4vs 71YvptZfks4JDCT8tevgN+LzB/wWQ7nANsV4h64p0s/1P4kqlRtihc1XWwMmR6vOKEPE IXW/2rSh05eX3JswMxihwUL4zwOIDOOK/W7mfnwzM2psHYv07x+QoMj4ZeIduMN8w4mB KnQoDxxEX1dx/hqxXV4jen8228WXel3N9QbdVCAG3zxgeDTTmPqOkIEW9uod4TbYZhUx VfzQ== X-Gm-Message-State: AOAM533jFLj4kbou/A+uBxuoMDrCviBd1V/tuMB5a3jbgmttt4Io99mi opERoSBtOQyhMq/N95P1lQuYWRMR3tw1/paP+DsfKdEqKKoOnJNoQyAny+Nm8i/7qnIz4s2Hofu V9LgVR7yYH/Uq6YvV2SBzakCu++h6 X-Received: by 2002:a0c:a802:: with SMTP id w2mr1345932qva.9.1606306481520; Wed, 25 Nov 2020 04:14:41 -0800 (PST) X-Google-Smtp-Source: ABdhPJzd8me3OtSowApCvc1hz6io7NTPHg4CrJj45yH6wBfmBDAx+yL2zySfQm4ED57QCMTJdKae9z/q4HcSu554TUY= X-Received: by 2002:a0c:a802:: with SMTP id w2mr1345902qva.9.1606306481218; Wed, 25 Nov 2020 04:14:41 -0800 (PST) MIME-Version: 1.0 References: <20201120185105.279030-1-eperezma@redhat.com> <5a4d0b7a-fb62-9e78-9e85-9262dca57f1c@redhat.com> In-Reply-To: From: Eugenio Perez Martin Date: Wed, 25 Nov 2020 13:14:05 +0100 Message-ID: Subject: Re: [RFC PATCH 00/27] vDPA software assisted live migration To: Jason Wang Cc: qemu-level , Lars Ganrot , virtualization@lists.linux-foundation.org, Salil Mehta , "Michael S. Tsirkin" , Liran Alon , Rob Miller , Max Gurtovoy , Alex Barba , Stefan Hajnoczi , Jim Harford , Harpreet Singh Anand , Christophe Fontaine , vm , Daniel Daly , Michael Lilja , Stefano Garzarella , Nitin Shrivastav , Lee Ballard , Dmytro Kazantsev , Juan Quintela , kvm list , Howard Cai , Xiao W Wang , Sean Mooney , Parav Pandit , Eli Cohen , Siwei Liu , Stephen Finucane Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, Nov 25, 2020 at 1:03 PM Eugenio Perez Martin wrote: > > On Wed, Nov 25, 2020 at 8:09 AM Jason Wang wrote: > > > > > > On 2020/11/21 =E4=B8=8A=E5=8D=882:50, Eugenio P=C3=A9rez wrote: > > > This series enable vDPA software assisted live migration for vhost-ne= t > > > devices. This is a new method of vhost devices migration: Instead of > > > relay on vDPA device's dirty logging capability, SW assisted LM > > > intercepts dataplane, forwarding the descriptors between VM and devic= e. > > > > > > In this migration mode, qemu offers a new vring to the device to > > > read and write into, and disable vhost notifiers, processing guest an= d > > > vhost notifications in qemu. On used buffer relay, qemu will mark the > > > dirty memory as with plain virtio-net devices. This way, devices does > > > not need to have dirty page logging capability. > > > > > > This series is a POC doing SW LM for vhost-net devices, which already > > > have dirty page logging capabilities. None of the changes have actual > > > effect with current devices until last two patches (26 and 27) are > > > applied, but they can be rebased on top of any other. These checks th= e > > > device to meet all requirements, and disable vhost-net devices loggin= g > > > so migration goes through SW LM. This last patch is not meant to be > > > applied in the final revision, it is in the series just for testing > > > purposes. > > > > > > For use SW assisted LM these vhost-net devices need to be instantiate= d: > > > * With IOMMU (iommu_platform=3Don,ats=3Don) > > > * Without event_idx (event_idx=3Doff) > > > > > > So a question is at what level do we want to implement qemu assisted > > live migration. To me it could be done at two levels: > > > > 1) generic vhost level which makes it work for both vhost-net/vhost-use= r > > and vhost-vDPA > > 2) a specific type of vhost > > > > To me, having a generic one looks better but it would be much more > > complicated. So what I read from this series is it was a vhost kernel > > specific software assisted live migration which is a good start. > > Actually it may even have real use case, e.g it can save dirty bitmaps > > for guest with large memory. But we need to address the above > > limitations first. > > > > So I would like to know what's the reason for mandating iommu platform > > and ats? And I think we need to fix case of event idx support. > > > > There is no specific reason for mandating iommu & ats, it was just > started that way. > > I will extend the patch to support those cases too. > > > > > > > > > Just the notification forwarding (with no descriptor relay) can be > > > achieved with patches 7 and 9, and starting migration. Partial applie= s > > > between 13 and 24 will not work while migrating on source, and patch > > > 25 is needed for the destination to resume network activity. > > > > > > It is based on the ideas of DPDK SW assisted LM, in the series of > > > > > > Actually we're better than that since there's no need the trick like > > hardcoded IOVA for mediated(shadow) virtqueue. > > > > > > > DPDK's https://patchwork.dpdk.org/cover/48370/ . > > > > > > I notice that you do GPA->VA translations and try to establish a VA->VA > > (use VA as IOVA) mapping via device IOTLB. This shortcut should work fo= r > > vhost-kernel/user but not vhost-vDPA. The reason is that there's no > > guarantee that the whole 64bit address range could be used as IOVA. One > > example is that for hardware IOMMU like intel, it usually has 47 or 52 > > bits of address width. > > > > So we probably need an IOVA allocator that can make sure the IOVA is no= t > > overlapped and fit for [1]. We can probably build the IOVA for guest VA > > via memory listeners. Then we have > > > > 1) IOVA for GPA > > 2) IOVA for shadow VQ > > > > And advertise IOVA to VA mapping to vhost. > > > > [1] > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/comm= it/?id=3D1b48dc03e575a872404f33b04cd237953c5d7498 > > > > Got it, will control it too. > > Maybe for vhost-net we could directly send iotlb miss for [0,~0ULL]. > Sorry, this was intended to be a question :). Given a vhost-* device IOVA usable range, is ok to expose all of qemu overlapping VA to it? With the iotlb miss, for example. Would it be acceptable from a security point of view? The device would have access to all qemu VA, but on the other hand devices like vhost-net already have it. > > > > > > > > Comments are welcome. > > > > > > Thanks! > > > > > > Eugenio P=C3=A9rez (27): > > > vhost: Add vhost_dev_can_log > > > vhost: Add device callback in vhost_migration_log > > > vhost: Move log resize/put to vhost_dev_set_log > > > vhost: add vhost_kernel_set_vring_enable > > > vhost: Add hdev->dev.sw_lm_vq_handler > > > virtio: Add virtio_queue_get_used_notify_split > > > vhost: Route guest->host notification through qemu > > > vhost: Add a flag for software assisted Live Migration > > > vhost: Route host->guest notification through qemu > > > vhost: Allocate shadow vring > > > virtio: const-ify all virtio_tswap* functions > > > virtio: Add virtio_queue_full > > > vhost: Send buffers to device > > > virtio: Remove virtio_queue_get_used_notify_split > > > vhost: Do not invalidate signalled used > > > virtio: Expose virtqueue_alloc_element > > > vhost: add vhost_vring_set_notification_rcu > > > vhost: add vhost_vring_poll_rcu > > > vhost: add vhost_vring_get_buf_rcu > > > vhost: Return used buffers > > > vhost: Add vhost_virtqueue_memory_unmap > > > vhost: Add vhost_virtqueue_memory_map > > > vhost: unmap qemu's shadow virtqueues on sw live migration > > > vhost: iommu changes > > > vhost: Do not commit vhost used idx on vhost_virtqueue_stop > > > vhost: Add vhost_hdev_can_sw_lm > > > vhost: forbid vhost devices logging > > > > > > hw/virtio/vhost-sw-lm-ring.h | 39 +++ > > > include/hw/virtio/vhost.h | 5 + > > > include/hw/virtio/virtio-access.h | 8 +- > > > include/hw/virtio/virtio.h | 4 + > > > hw/net/virtio-net.c | 39 ++- > > > hw/virtio/vhost-backend.c | 29 ++ > > > hw/virtio/vhost-sw-lm-ring.c | 268 +++++++++++++++++++ > > > hw/virtio/vhost.c | 431 +++++++++++++++++++++++++--= --- > > > hw/virtio/virtio.c | 18 +- > > > hw/virtio/meson.build | 2 +- > > > 10 files changed, 758 insertions(+), 85 deletions(-) > > > create mode 100644 hw/virtio/vhost-sw-lm-ring.h > > > create mode 100644 hw/virtio/vhost-sw-lm-ring.c > > > > > > So this looks like a pretty huge patchset which I'm trying to think of > > ways to split. An idea is to do this is two steps > > > > 1) implement a shadow virtqueue mode for vhost first (w/o live > > migration). Then we can test descriptors relay, IOVA allocating, etc. > > How would that mode be activated if it is not tied to live migration? > New backend/command line switch? > > Maybe it is better to also start with no iommu & ats support and add it o= n top. > > > 2) add live migration support on top > > > > And it looks to me it's better to split the shadow virtqueue (virtio > > driver part) into an independent file. And use generic name (w/o > > "shadow") in order to be reused by other use cases as well. > > > > I think the same. > > Thanks! > > > Thoughts? > >