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strparser: pad sk_skb_cb to avoid straddling cachelines 

Tested: selftests
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2143700

commit 2d91ecace6614cf6254001566292b808d7f70a91
Author: Jakub Kicinski <kuba@kernel.org>
Date:   Thu Jul 7 18:03:09 2022 -0700

    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>

Signed-off-by: Sabrina Dubroca <sdubroca@redhat.com>
This commit is contained in:
Sabrina Dubroca 2022-11-30 23:43:02 +01:00
parent c92a443dc7
commit 90cfe62767
2 changed files with 11 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

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;