Re: [PATCH v1] vdpa/mlx5: Add support for doorbell bypassing

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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 <elic@xxxxxxxxxx>
---
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;
   }

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