linux-kernel - [PATCH 1/2] vdpa/mlx5: Support creating resources with uid == 0

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Date:   Sun, 30 May 2021 10:54:14 +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 1/2] vdpa/mlx5: Support creating resources with uid == 0

Currently all resources must be created with uid != 0 which is essential
userspace processes allocating virtquueue resources. Since this is a
kernel implementation, it is perfectly legal to open resources with
uid == 0.

In case frimware supports, avoid allocating user context.

Signed-off-by: Eli Cohen <elic@...dia.com>
---
 drivers/vdpa/mlx5/core/resources.c | 6 ++++++
 include/linux/mlx5/mlx5_ifc.h      | 4 +++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/vdpa/mlx5/core/resources.c b/drivers/vdpa/mlx5/core/resources.c
index 6521cbd0f5c2..836ab9ef0fa6 100644
--- a/drivers/vdpa/mlx5/core/resources.c
+++ b/drivers/vdpa/mlx5/core/resources.c
@@ -54,6 +54,9 @@ static int create_uctx(struct mlx5_vdpa_dev *mvdev, u16 *uid)
 	void *in;
 	int err;
 
+	if (MLX5_CAP_GEN(mvdev->mdev, umem_uid_0))
+		return 0;
+
 	/* 0 means not supported */
 	if (!MLX5_CAP_GEN(mvdev->mdev, log_max_uctx))
 		return -EOPNOTSUPP;
@@ -79,6 +82,9 @@ static void destroy_uctx(struct mlx5_vdpa_dev *mvdev, u32 uid)
 	u32 out[MLX5_ST_SZ_DW(destroy_uctx_out)] = {};
 	u32 in[MLX5_ST_SZ_DW(destroy_uctx_in)] = {};
 
+	if (!uid)
+		return;
+
 	MLX5_SET(destroy_uctx_in, in, opcode, MLX5_CMD_OP_DESTROY_UCTX);
 	MLX5_SET(destroy_uctx_in, in, uid, uid);
 
diff --git a/include/linux/mlx5/mlx5_ifc.h b/include/linux/mlx5/mlx5_ifc.h
index 9c68b2da14c6..606d2aeacad4 100644
--- a/include/linux/mlx5/mlx5_ifc.h
+++ b/include/linux/mlx5/mlx5_ifc.h
@@ -1487,7 +1487,9 @@ struct mlx5_ifc_cmd_hca_cap_bits {
 	u8         uar_4k[0x1];
 	u8         reserved_at_241[0x9];
 	u8         uar_sz[0x6];
-	u8         reserved_at_250[0x8];
+	u8         reserved_at_248[0x2];
+	u8         umem_uid_0[0x1];
+	u8         reserved_at_250[0x5];
 	u8         log_pg_sz[0x8];
 
 	u8         bf[0x1];
-- 
2.31.1