linux-kernel - [PATCH v2] vdpa/mlx5: Add support for doorbell bypassing

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Date:   Thu, 3 Jun 2021 11:11:53 +0300
From:   Eli Cohen <elic@...dia.com>
To:     <mst@...hat.com>, <jasowang@...hat.com>,
        <virtualization@...ts.linux-foundation.org>,
        <linux-kernel@...r.kernel.org>
CC:     <elic@...dia.com>
Subject: [PATCH v2] vdpa/mlx5: Add support for doorbell bypassing

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@...dia.com>
---
v0 --> v1:
  Make sure SF bar size is not smaller than PAGE_SIZE
v1 --> v2:
  Remove test on addr alignment since it's alrady done by the caller.

 drivers/vdpa/mlx5/core/mlx5_vdpa.h |  1 +
 drivers/vdpa/mlx5/core/resources.c |  1 +
 drivers/vdpa/mlx5/net/mlx5_vnet.c  | 14 ++++++++++++++
 3 files changed, 16 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 689d3fa61e08..bc33f2c523d3 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
@@ -1879,8 +1879,22 @@ 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;
+	ret.addr = addr;
+	ret.size = PAGE_SIZE;
 	return ret;
 }
 
-- 
2.31.1