[PATCH] vdpa/mlx5: Use kvzalloc_flex() for MTT command memory

[Rosen Penev <rosenp@gmail.com>]

The create mkey command memory embeds the MTT array as a flexible array
member. Use kvzalloc_flex() to allocate it directly instead of open-coding
the struct_size() calculation with kvcalloc().

The MTT allocation still needs to be aligned to MLX5_VDPA_MTT_ALIGN bytes.
Since each MTT entry is __be64, align the entry count directly and avoid
carrying a separate byte length variable.

Assisted-by: Codex:GPT-5.5
Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 drivers/vdpa/mlx5/core/mr.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/vdpa/mlx5/core/mr.c b/drivers/vdpa/mlx5/core/mr.c
index 42c2705077a6..6d02ccf9eb91 100644
--- a/drivers/vdpa/mlx5/core/mr.c
+++ b/drivers/vdpa/mlx5/core/mr.c
@@ -221,11 +221,10 @@ static int create_direct_keys(struct mlx5_vdpa_dev *mvdev, struct mlx5_vdpa_mr *
 
 	list_for_each_entry(dmr, &mr->head, list) {
 		struct mlx5_create_mkey_mem *cmd_mem;
-		int mttlen, mttcount;
+		int mttcount;
 
-		mttlen = roundup(MLX5_ST_SZ_BYTES(mtt) * dmr->nsg, MLX5_VDPA_MTT_ALIGN);
-		mttcount = mttlen / sizeof(cmd_mem->mtt[0]);
-		cmd_mem = kvcalloc(1, struct_size(cmd_mem, mtt, mttcount), GFP_KERNEL);
+		mttcount = ALIGN(dmr->nsg, MLX5_VDPA_MTT_ALIGN / sizeof(cmd_mem->mtt[0]));
+		cmd_mem = kvzalloc_flex(*cmd_mem, mtt, mttcount);
 		if (!cmd_mem) {
 			err = -ENOMEM;
 			goto done;
-- 
2.54.0