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strparser: pad sk_skb_cb to avoid straddling cachelines 

sk_skb_cb lives within skb->cb[]. skb->cb[] straddles
2 cache lines, each containing 24B of data.
The first cache line does not contain much interesting
information for users of strparser, so pad things a little.
Previously strp_msg->full_len would live in the first cache
line and strp_msg->offset in the second.

We need to reorder the 8 byte temp_reg with struct tls_msg
to prevent a 4B hole which would push the struct over 48B.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski 2022-07-07 18:03:09 -07:00
parent 67d7ebdeb2
commit 2d91ecace6
2 changed files with 11 additions and 4 deletions
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12
include/net/strparser.h
View File

@ -65,15 +65,19 @@ struct _strp_msg {
struct sk_skb_cb {
#define SK_SKB_CB_PRIV_LEN 20
unsigned char data[SK_SKB_CB_PRIV_LEN];
/* align strp on cache line boundary within skb->cb[] */
unsigned char pad[4];
struct _strp_msg strp;
/* temp_reg is a temporary register used for bpf_convert_data_end_access
* when dst_reg == src_reg.
*/
u64 temp_reg;
/* strp users' data follows */
struct tls_msg {
u8 control;
u8 decrypted;
} tls;
/* temp_reg is a temporary register used for bpf_convert_data_end_access
* when dst_reg == src_reg.
*/
u64 temp_reg;
};
static inline struct strp_msg *strp_msg(struct sk_buff *skb)

3
net/strparser/strparser.c
View File

@ -533,6 +533,9 @@ EXPORT_SYMBOL_GPL(strp_check_rcv);
static int __init strp_dev_init(void)
{
BUILD_BUG_ON(sizeof(struct sk_skb_cb) >
sizeof_field(struct sk_buff, cb));
strp_wq = create_singlethread_workqueue("kstrp");
if (unlikely(!strp_wq))
return -ENOMEM;