From: "Michael S. Tsirkin" <[email protected]>
Changing alignment of header would mean it's no longer safe to cast a
2 byte aligned pointer between formats. Use two 16 bit fields to make
it 2 byte aligned as previously.
This fixes the performance regression since
commit ("virtio_net: enable gso over UDP tunnel support.") as it uses
virtio_net_hdr_v1_hash_tunnel which embeds
virtio_net_hdr_v1_hash. Pktgen in guest + XDP_DROP on TAP + vhost_net
shows the TX PPS is recovered from 2.4Mpps to 4.45Mpps.
Fixes: 56a06bd40fab ("virtio_net: enable gso over UDP tunnel support.")
Cc: [email protected]
Signed-off-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Jason Wang <[email protected]>
---
Changes since V1:
- Fix build issues of virtio_net_hdr_tnl_from_skb()
---
drivers/net/virtio_net.c | 15 +++++++++++++--
include/linux/virtio_net.h | 3 ++-
include/uapi/linux/virtio_net.h | 3 ++-
3 files changed, 17 insertions(+), 4 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 8e8a179aaa49..e6e650bc3bc3 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2539,6 +2539,13 @@ static struct sk_buff *receive_mergeable(struct
net_device *dev,
return NULL;
}
+static inline u32
+virtio_net_hash_value(const struct virtio_net_hdr_v1_hash *hdr_hash)
+{
+ return __le16_to_cpu(hdr_hash->hash_value_lo) |
+ (__le16_to_cpu(hdr_hash->hash_value_hi) << 16);
+}
+
static void virtio_skb_set_hash(const struct virtio_net_hdr_v1_hash *hdr_hash,
struct sk_buff *skb)
{
@@ -2565,7 +2572,7 @@ static void virtio_skb_set_hash(const struct
virtio_net_hdr_v1_hash *hdr_hash,
default:
rss_hash_type = PKT_HASH_TYPE_NONE;
}
- skb_set_hash(skb, __le32_to_cpu(hdr_hash->hash_value), rss_hash_type);
+ skb_set_hash(skb, virtio_net_hash_value(hdr_hash), rss_hash_type);
}
static void virtnet_receive_done(struct virtnet_info *vi, struct receive_queue
*rq,
@@ -3311,6 +3318,10 @@ static int xmit_skb(struct send_queue *sq, struct
sk_buff *skb, bool orphan)
pr_debug("%s: xmit %p %pM\n", vi->dev->name, skb, dest);
+ /* Make sure it's safe to cast between formats */
+ BUILD_BUG_ON(__alignof__(*hdr) != __alignof__(hdr->hash_hdr));
+ BUILD_BUG_ON(__alignof__(*hdr) != __alignof__(hdr->hash_hdr.hdr));
+
can_push = vi->any_header_sg &&
!((unsigned long)skb->data & (__alignof__(*hdr) - 1)) &&
!skb_header_cloned(skb) && skb_headroom(skb) >= hdr_len;
@@ -6750,7 +6761,7 @@ static int virtnet_xdp_rx_hash(const struct xdp_md *_ctx,
u32 *hash,
hash_report = VIRTIO_NET_HASH_REPORT_NONE;
*rss_type = virtnet_xdp_rss_type[hash_report];
- *hash = __le32_to_cpu(hdr_hash->hash_value);
+ *hash = virtio_net_hash_value(hdr_hash);
return 0;
}
diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index 4d1780848d0e..b673c31569f3 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -401,7 +401,8 @@ virtio_net_hdr_tnl_from_skb(const struct sk_buff *skb,
if (!tnl_hdr_negotiated)
return -EINVAL;
- vhdr->hash_hdr.hash_value = 0;
+ vhdr->hash_hdr.hash_value_lo = 0;
+ vhdr->hash_hdr.hash_value_hi = 0;
vhdr->hash_hdr.hash_report = 0;
vhdr->hash_hdr.padding = 0;
diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
index 8bf27ab8bcb4..1db45b01532b 100644
--- a/include/uapi/linux/virtio_net.h
+++ b/include/uapi/linux/virtio_net.h
@@ -193,7 +193,8 @@ struct virtio_net_hdr_v1 {
struct virtio_net_hdr_v1_hash {
struct virtio_net_hdr_v1 hdr;
- __le32 hash_value;
+ __le16 hash_value_lo;
+ __le16 hash_value_hi;
#define VIRTIO_NET_HASH_REPORT_NONE 0
#define VIRTIO_NET_HASH_REPORT_IPv4 1
#define VIRTIO_NET_HASH_REPORT_TCPv4 2
--
2.31.1
