mlxsw: spectrum_buffers: Reject overlarge headroom size requests

cap_max_headroom_size holds maximum headroom size supported.
Overstepping that limit might under certain conditions lead to ASIC
freeze.

Query and store the value, and add mlxsw_sp_sb_max_headroom_cells() for
obtaining the stored value. In __mlxsw_sp_port_headroom_set(), reject
requests where the total port buffer is larger than the advertised
maximum.

Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/resources.h

@@ -26,6 +26,7 @@ enum mlxsw_res_id {
 	MLXSW_RES_ID_MAX_LAG_MEMBERS,
 	MLXSW_RES_ID_MAX_BUFFER_SIZE,
 	MLXSW_RES_ID_CELL_SIZE,
+	MLXSW_RES_ID_MAX_HEADROOM_SIZE,
 	MLXSW_RES_ID_ACL_MAX_TCAM_REGIONS,
 	MLXSW_RES_ID_ACL_MAX_TCAM_RULES,
 	MLXSW_RES_ID_ACL_MAX_REGIONS,
@@ -79,6 +80,7 @@ static u16 mlxsw_res_ids[] = {
 	[MLXSW_RES_ID_MAX_LAG_MEMBERS] = 0x2521,
 	[MLXSW_RES_ID_MAX_BUFFER_SIZE] = 0x2802,	/* Bytes */
 	[MLXSW_RES_ID_CELL_SIZE] = 0x2803,	/* Bytes */
+	[MLXSW_RES_ID_MAX_HEADROOM_SIZE] = 0x2811,	/* Bytes */
 	[MLXSW_RES_ID_ACL_MAX_TCAM_REGIONS] = 0x2901,
 	[MLXSW_RES_ID_ACL_MAX_TCAM_RULES] = 0x2902,
 	[MLXSW_RES_ID_ACL_MAX_REGIONS] = 0x2903,

drivers/net/ethernet/mellanox/mlxsw/spectrum.c

@@ -852,8 +852,12 @@ int __mlxsw_sp_port_headroom_set(struct mlxsw_sp_port *mlxsw_sp_port, int mtu,
 	u8 pfc_en = !!my_pfc ? my_pfc->pfc_en : 0;
 	u16 delay = !!my_pfc ? my_pfc->delay : 0;
 	char pbmc_pl[MLXSW_REG_PBMC_LEN];
+	u32 taken_headroom_cells = 0;
+	u32 max_headroom_cells;
 	int i, j, err;
 
+	max_headroom_cells = mlxsw_sp_sb_max_headroom_cells(mlxsw_sp);
+
 	mlxsw_reg_pbmc_pack(pbmc_pl, mlxsw_sp_port->local_port, 0, 0);
 	err = mlxsw_reg_query(mlxsw_sp->core, MLXSW_REG(pbmc), pbmc_pl);
 	if (err)
@@ -864,6 +868,7 @@ int __mlxsw_sp_port_headroom_set(struct mlxsw_sp_port *mlxsw_sp_port, int mtu,
 		bool pfc = false;
 		u16 thres_cells;
 		u16 delay_cells;
+		u16 total_cells;
 		bool lossy;
 
 		for (j = 0; j < IEEE_8021QAZ_MAX_TCS; j++) {
@@ -881,7 +886,13 @@ int __mlxsw_sp_port_headroom_set(struct mlxsw_sp_port *mlxsw_sp_port, int mtu,
 		thres_cells = mlxsw_sp_pg_buf_threshold_get(mlxsw_sp, mtu);
 		delay_cells = mlxsw_sp_pg_buf_delay_get(mlxsw_sp, mtu, delay,
 							pfc, pause_en);
-		mlxsw_sp_pg_buf_pack(pbmc_pl, i, thres_cells + delay_cells,
+		total_cells = thres_cells + delay_cells;
+
+		taken_headroom_cells += total_cells;
+		if (taken_headroom_cells > max_headroom_cells)
+			return -ENOBUFS;
+
+		mlxsw_sp_pg_buf_pack(pbmc_pl, i, total_cells,
 				     thres_cells, lossy);
 	}
 

drivers/net/ethernet/mellanox/mlxsw/spectrum.h

@@ -373,6 +373,7 @@ int mlxsw_sp_sb_occ_tc_port_bind_get(struct mlxsw_core_port *mlxsw_core_port,
 				     u32 *p_cur, u32 *p_max);
 u32 mlxsw_sp_cells_bytes(const struct mlxsw_sp *mlxsw_sp, u32 cells);
 u32 mlxsw_sp_bytes_cells(const struct mlxsw_sp *mlxsw_sp, u32 bytes);
+u32 mlxsw_sp_sb_max_headroom_cells(const struct mlxsw_sp *mlxsw_sp);
 
 extern const struct mlxsw_sp_sb_vals mlxsw_sp1_sb_vals;
 extern const struct mlxsw_sp_sb_vals mlxsw_sp2_sb_vals;

drivers/net/ethernet/mellanox/mlxsw/spectrum_buffers.c

@@ -85,6 +85,7 @@ struct mlxsw_sp_sb {
 	struct mlxsw_sp_sb_pr *prs;
 	struct mlxsw_sp_sb_port *ports;
 	u32 cell_size;
+	u32 max_headroom_cells;
 	u64 sb_size;
 };
 
@@ -113,6 +114,11 @@ u32 mlxsw_sp_bytes_cells(const struct mlxsw_sp *mlxsw_sp, u32 bytes)
 	return DIV_ROUND_UP(bytes, mlxsw_sp->sb->cell_size);
 }
 
+u32 mlxsw_sp_sb_max_headroom_cells(const struct mlxsw_sp *mlxsw_sp)
+{
+	return mlxsw_sp->sb->max_headroom_cells;
+}
+
 static struct mlxsw_sp_sb_pr *mlxsw_sp_sb_pr_get(struct mlxsw_sp *mlxsw_sp,
 						 u16 pool_index)
 {
@@ -789,6 +795,7 @@ const struct mlxsw_sp_sb_vals mlxsw_sp2_sb_vals = {
 
 int mlxsw_sp_buffers_init(struct mlxsw_sp *mlxsw_sp)
 {
+	u32 max_headroom_size;
 	u16 ing_pool_count;
 	u16 eg_pool_count;
 	int err;
@@ -799,12 +806,21 @@ int mlxsw_sp_buffers_init(struct mlxsw_sp *mlxsw_sp)
 	if (!MLXSW_CORE_RES_VALID(mlxsw_sp->core, MAX_BUFFER_SIZE))
 		return -EIO;
 
+	if (!MLXSW_CORE_RES_VALID(mlxsw_sp->core, MAX_HEADROOM_SIZE))
+		return -EIO;
+
 	mlxsw_sp->sb = kzalloc(sizeof(*mlxsw_sp->sb), GFP_KERNEL);
 	if (!mlxsw_sp->sb)
 		return -ENOMEM;
 	mlxsw_sp->sb->cell_size = MLXSW_CORE_RES_GET(mlxsw_sp->core, CELL_SIZE);
 	mlxsw_sp->sb->sb_size = MLXSW_CORE_RES_GET(mlxsw_sp->core,
 						   MAX_BUFFER_SIZE);
+	max_headroom_size = MLXSW_CORE_RES_GET(mlxsw_sp->core,
+					       MAX_HEADROOM_SIZE);
+	/* Round down, because this limit must not be overstepped. */
+	mlxsw_sp->sb->max_headroom_cells = max_headroom_size /
+						mlxsw_sp->sb->cell_size;
+
 	err = mlxsw_sp_sb_ports_init(mlxsw_sp);
 	if (err)
 		goto err_sb_ports_init;