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=-17.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 876A4C433B4 for ; Thu, 22 Apr 2021 04:52:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5EA136141C for ; Thu, 22 Apr 2021 04:52:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229709AbhDVEw6 (ORCPT ); Thu, 22 Apr 2021 00:52:58 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:30126 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229533AbhDVEw4 (ORCPT ); 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Thu, 22 Apr 2021 04:52:18 +0000 (UTC) Received: from wangxiaodeMacBook-Air.local (ovpn-13-214.pek2.redhat.com [10.72.13.214]) by smtp.corp.redhat.com (Postfix) with ESMTP id 61A5662693; Thu, 22 Apr 2021 04:52:11 +0000 (UTC) Subject: Re: [PATCH] vdpa/mlx5: Add support for doorbell bypassing To: =?UTF-8?Q?Mika_Penttil=c3=a4?= , Eli Cohen , mst@redhat.com Cc: virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org References: <20210421104145.115907-1-elic@nvidia.com> From: Jason Wang Message-ID: <7bdb251a-5e16-dd22-d204-6ff57e12e72f@redhat.com> Date: Thu, 22 Apr 2021 12:52:09 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2021/4/22 上午11:27, Mika Penttilä 写道: > > > On 22.4.2021 5.37, Jason Wang wrote: >> >> 在 2021/4/21 下午6:41, Eli Cohen 写道: >>> Implement mlx5_get_vq_notification() to return the doorbell address. >>> Size is set to one system page as required. >>> >>> Signed-off-by: Eli Cohen >>> --- >>>   drivers/vdpa/mlx5/core/mlx5_vdpa.h | 1 + >>>   drivers/vdpa/mlx5/core/resources.c | 1 + >>>   drivers/vdpa/mlx5/net/mlx5_vnet.c  | 6 ++++++ >>>   3 files changed, 8 insertions(+) >>> >>> diff --git a/drivers/vdpa/mlx5/core/mlx5_vdpa.h >>> b/drivers/vdpa/mlx5/core/mlx5_vdpa.h >>> index b6cc53ba980c..49de62cda598 100644 >>> --- a/drivers/vdpa/mlx5/core/mlx5_vdpa.h >>> +++ b/drivers/vdpa/mlx5/core/mlx5_vdpa.h >>> @@ -41,6 +41,7 @@ struct mlx5_vdpa_resources { >>>       u32 pdn; >>>       struct mlx5_uars_page *uar; >>>       void __iomem *kick_addr; >>> +    u64 phys_kick_addr; >>>       u16 uid; >>>       u32 null_mkey; >>>       bool valid; >>> diff --git a/drivers/vdpa/mlx5/core/resources.c >>> b/drivers/vdpa/mlx5/core/resources.c >>> index 6521cbd0f5c2..665f8fc1710f 100644 >>> --- a/drivers/vdpa/mlx5/core/resources.c >>> +++ b/drivers/vdpa/mlx5/core/resources.c >>> @@ -247,6 +247,7 @@ int mlx5_vdpa_alloc_resources(struct >>> mlx5_vdpa_dev *mvdev) >>>           goto err_key; >>>         kick_addr = mdev->bar_addr + offset; >>> +    res->phys_kick_addr = kick_addr; >>>         res->kick_addr = ioremap(kick_addr, PAGE_SIZE); >>>       if (!res->kick_addr) { >>> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c >>> b/drivers/vdpa/mlx5/net/mlx5_vnet.c >>> index 10c5fef3c020..680751074d2a 100644 >>> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c >>> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c >>> @@ -1865,8 +1865,14 @@ static void mlx5_vdpa_free(struct vdpa_device >>> *vdev) >>>     static struct vdpa_notification_area >>> mlx5_get_vq_notification(struct vdpa_device *vdev, u16 idx) >>>   { >>> +    struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev); >>>       struct vdpa_notification_area ret = {}; >>> +    struct mlx5_vdpa_net *ndev; >>> + >>> +    ndev = to_mlx5_vdpa_ndev(mvdev); >>>   +    ret.addr = (phys_addr_t)ndev->mvdev.res.phys_kick_addr; >>> +    ret.size = PAGE_SIZE; >> >> >> Note that the page will be mapped in to guest, so it's only safe if >> the doorbeel exclusively own the page. This means if there're other >> registers in the page, we can not let the doorbell bypass to work. >> >> So this is suspicious at least in the case of subfunction where we >> calculate the bar length in mlx5_sf_dev_table_create() as: >> >> table->sf_bar_length = 1 << (MLX5_CAP_GEN(dev, log_min_sf_size) + 12); >> >> It looks to me this can only work for the arch with PAGE_SIZE = 4096, >> otherwise we can map more into the userspace(guest). >> >> Thanks >> >> > Is there support as of today (in qemu  or elsewhere) to use this mmap > doorbell instead of the traditional kick. Vhost-user had already had this support in Qemu (see set_host_notifier_mr). And I've posted patches to support this for qemu[1] and vp_vdpa[2] driver. Thanks [1] https://www.mail-archive.com/qemu-devel@nongnu.org/msg798935.html [2] https://lore.kernel.org/virtualization/20210415073147.19331-5-jasowang@redhat.com/T/ > > --Mika > > > >> >>>       return ret; >>>   } >> >