Fri, Feb 17, 2023 at 01:22:01PM CET, mst@xxxxxxxxxx wrote:
>On Fri, Feb 17, 2023 at 01:15:47PM +0100, Jiri Pirko wrote:
>> From: Jiri Pirko <jiri@xxxxxxxxxx>
>>
>> virtio_net_hdr_from_skb() fills up hdr_len to skb_headlen(skb).
>>
>> Virtio spec introduced a feature VIRTIO_NET_F_GUEST_HDRLEN which when
>> set implicates that the driver provides the exact size of the header.
>>
>> The driver already complies to fill the correct value. Introduce the
>> feature and advertise it.
>>
>> Signed-off-by: Jiri Pirko <jiri@xxxxxxxxxx>
>
>Could you add a bit of motivation just for the record?
>Does this improve performance for some card? By how much?
>Expected to help some future card?
I can get that info, but isn't that rather something to be appended to
the virtio-spec patch? I mean, the feature is there, this is just
implementing it in one driver.
>
>thanks!
>
>
>> ---
>> drivers/net/virtio_net.c | 6 ++++--
>> include/uapi/linux/virtio_net.h | 1 +
>> 2 files changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index fb5e68ed3ec2..e85b03988733 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -62,7 +62,8 @@ static const unsigned long guest_offloads[] = {
>> VIRTIO_NET_F_GUEST_UFO,
>> VIRTIO_NET_F_GUEST_CSUM,
>> VIRTIO_NET_F_GUEST_USO4,
>> - VIRTIO_NET_F_GUEST_USO6
>> + VIRTIO_NET_F_GUEST_USO6,
>> + VIRTIO_NET_F_GUEST_HDRLEN
>> };
>>
>> #define GUEST_OFFLOAD_GRO_HW_MASK ((1ULL << VIRTIO_NET_F_GUEST_TSO4) | \
>> @@ -4213,7 +4214,8 @@ static struct virtio_device_id id_table[] = {
>> VIRTIO_NET_F_CTRL_MAC_ADDR, \
>> VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS, \
>> VIRTIO_NET_F_SPEED_DUPLEX, VIRTIO_NET_F_STANDBY, \
>> - VIRTIO_NET_F_RSS, VIRTIO_NET_F_HASH_REPORT, VIRTIO_NET_F_NOTF_COAL
>> + VIRTIO_NET_F_RSS, VIRTIO_NET_F_HASH_REPORT, VIRTIO_NET_F_NOTF_COAL, \
>> + VIRTIO_NET_F_GUEST_HDRLEN
>>
>> static unsigned int features[] = {
>> VIRTNET_FEATURES,
>> diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
>> index b4062bed186a..12c1c9699935 100644
>> --- a/include/uapi/linux/virtio_net.h
>> +++ b/include/uapi/linux/virtio_net.h
>> @@ -61,6 +61,7 @@
>> #define VIRTIO_NET_F_GUEST_USO6 55 /* Guest can handle USOv6 in. */
>> #define VIRTIO_NET_F_HOST_USO 56 /* Host can handle USO in. */
>> #define VIRTIO_NET_F_HASH_REPORT 57 /* Supports hash report */
>> +#define VIRTIO_NET_F_GUEST_HDRLEN 59 /* Guest provides the exact hdr_len value. */
>> #define VIRTIO_NET_F_RSS 60 /* Supports RSS RX steering */
>> #define VIRTIO_NET_F_RSC_EXT 61 /* extended coalescing info */
>> #define VIRTIO_NET_F_STANDBY 62 /* Act as standby for another device
>> --
>> 2.39.0
>
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