Patch "IB/core: Fix ib_wc structure size to remain in 64 bytes boundary" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

IB/core: Fix ib_wc structure size to remain in 64 bytes boundary

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ib-core-fix-ib_wc-structure-size-to-remain-in-64-bytes-boundary.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Bodong Wang <[email protected]>
Date: Fri, 12 Jan 2018 07:58:41 +0200
Subject: IB/core: Fix ib_wc structure size to remain in 64 bytes boundary

From: Bodong Wang <[email protected]>

commit cd2a6e7d384b043d5d029e39663061cebc949385 upstream.

The change of slid from u16 to u32 results in sizeof(struct ib_wc) cross 64B boundary, which causes more cache misses. This patch rearranges the fields and remain the size to 64B.

Pahole output before this change:

struct ib_wc {
union {
u64 wr_id; /* 8 */
struct ib_cqe * wr_cqe; /* 8 */
}; /* 0 8 */
enum ib_wc_status status; /* 8 4 */
enum ib_wc_opcode opcode; /* 12 4 */
u32 vendor_err; /* 16 4 */
u32 byte_len; /* 20 4 */
struct ib_qp * qp; /* 24 8 */
union {
__be32 imm_data; /* 4 */
u32 invalidate_rkey; /* 4 */
} ex; /* 32 4 */
u32 src_qp; /* 36 4 */
int wc_flags; /* 40 4 */
u16 pkey_index; /* 44 2 */

/* XXX 2 bytes hole, try to pack */

u32 slid; /* 48 4 */
u8 sl; /* 52 1 */
u8 dlid_path_bits; /* 53 1 */
u8 port_num; /* 54 1 */
u8 smac[6]; /* 55 6 */

/* XXX 1 byte hole, try to pack */

u16 vlan_id; /* 62 2 */
/* --- cacheline 1 boundary (64 bytes) --- */
u8 network_hdr_type; /* 64 1 */

/* size: 72, cachelines: 2, members: 17 */ /* sum members: 62, holes: 2, sum holes: 3 */ /* padding: 7 */
/* last cacheline: 8 bytes */
};

Pahole output after this change:

struct ib_wc {
union {
u64 wr_id; /* 8 */
struct ib_cqe * wr_cqe; /* 8 */
}; /* 0 8 */
enum ib_wc_status status; /* 8 4 */
enum ib_wc_opcode opcode; /* 12 4 */
u32 vendor_err; /* 16 4 */
u32 byte_len; /* 20 4 */
struct ib_qp * qp; /* 24 8 */
union {
__be32 imm_data; /* 4 */
u32 invalidate_rkey; /* 4 */
} ex; /* 32 4 */
u32 src_qp; /* 36 4 */
u32 slid; /* 40 4 */
int wc_flags; /* 44 4 */
u16 pkey_index; /* 48 2 */
u8 sl; /* 50 1 */
u8 dlid_path_bits; /* 51 1 */
u8 port_num; /* 52 1 */
u8 smac[6]; /* 53 6 */

/* XXX 1 byte hole, try to pack */

u16 vlan_id; /* 60 2 */
u8 network_hdr_type; /* 62 1 */

/* size: 64, cachelines: 1, members: 17 */ /* sum members: 62, holes: 1, sum holes: 1 */ /* padding: 1 */
};

---
 include/rdma/ib_verbs.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -971,9 +971,9 @@ struct ib_wc {
 		u32		invalidate_rkey;
 	} ex;
 	u32			src_qp;
+	u32			slid;
 	int			wc_flags;
 	u16			pkey_index;
-	u32			slid;
 	u8			sl;
 	u8			dlid_path_bits;
 	u8			port_num;	/* valid only for DR SMPs on switches */

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/ib-core-fix-ib_wc-structure-size-to-remain-in-64-bytes-boundary.patch