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Thu, 03 Jun 2021 00:49:08 -0700 (PDT) Received: from wangxiaodeMacBook-Air.local ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id a188sm1553571pfa.59.2021.06.03.00.49.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 03 Jun 2021 00:49:08 -0700 (PDT) Subject: Re: [PATCH v1] vdpa/mlx5: Add support for doorbell bypassing To: Eli Cohen Cc: mst@redhat.com, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org References: <20210602095358.83318-1-elic@nvidia.com> <20210603073840.GB58414@mtl-vdi-166.wap.labs.mlnx> From: Jason Wang Message-ID: <3ec31690-4cd8-1ea8-31dd-dfd3a8a25180@redhat.com> Date: Thu, 3 Jun 2021 15:49:04 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: <20210603073840.GB58414@mtl-vdi-166.wap.labs.mlnx> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2021/6/3 下午3:38, Eli Cohen 写道: > On Thu, Jun 03, 2021 at 03:11:51PM +0800, Jason Wang wrote: >> 在 2021/6/2 下午5:53, Eli Cohen 写道: >>> Implement mlx5_get_vq_notification() to return the doorbell address. >>> Since the notification area is mapped to userspace, make sure that the >>> BAR size is at least PAGE_SIZE large. >>> >>> Signed-off-by: Eli Cohen >>> --- >>> v0 --> v1: >>> Make sure SF bar size is not smaller than PAGE_SIZE >>> >>> drivers/vdpa/mlx5/core/mlx5_vdpa.h | 1 + >>> drivers/vdpa/mlx5/core/resources.c | 1 + >>> drivers/vdpa/mlx5/net/mlx5_vnet.c | 17 +++++++++++++++++ >>> 3 files changed, 19 insertions(+) >>> >>> diff --git a/drivers/vdpa/mlx5/core/mlx5_vdpa.h b/drivers/vdpa/mlx5/core/mlx5_vdpa.h >>> index 09a16a3d1b2a..0002b2136b48 100644 >>> --- a/drivers/vdpa/mlx5/core/mlx5_vdpa.h >>> +++ b/drivers/vdpa/mlx5/core/mlx5_vdpa.h >>> @@ -42,6 +42,7 @@ 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 836ab9ef0fa6..d4606213f88a 100644 >>> --- a/drivers/vdpa/mlx5/core/resources.c >>> +++ b/drivers/vdpa/mlx5/core/resources.c >>> @@ -253,6 +253,7 @@ 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 5500bcfe84b4..1936039e05bd 100644 >>> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c >>> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c >>> @@ -1871,8 +1871,25 @@ 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; >>> + phys_addr_t addr; >>> + >>> + /* If SF BAR size is smaller than PAGE_SIZE, do not use direct >>> + * notification to avoid the risk of mapping pages that contain BAR of more >>> + * than one SF >>> + */ >>> + if (MLX5_CAP_GEN(mvdev->mdev, log_min_sf_size) + 12 < PAGE_SHIFT) >>> + return ret; >>> + >>> + ndev = to_mlx5_vdpa_ndev(mvdev); >>> + addr = (phys_addr_t)ndev->mvdev.res.phys_kick_addr; >>> + if (addr & ~PAGE_MASK) >>> + return ret; >> >> This has been checked by vhost-vDPA, and it's better to leave those policy >> checking to them driver instead of checking it in the parent. >> > Not in all invocations of get_vq_notification(). For example, in > vhost_vdpa_fault() you call remap_pfn_range() with notify.addr >> > PAGE_SHIFT so it it was not aligned you mask this misalignment. In order to have vhost_vdpa_fault() works, it should first pass the check of vhost_vdpa_mmap(). Othewise we won't install vma->vm_ops so there won't be a page fault for the doorbell. Thanks > >> Thanks >> >> >>> + ret.addr = (phys_addr_t)ndev->mvdev.res.phys_kick_addr; >>> + ret.size = PAGE_SIZE; >>> return ret; >>> }