[...]
>> Perfect! hacking qemu for testing is no problem this helps a lot thanks
>> and saves me time trying to figure out how to get qemu to do this.
>
> Pls note I didn't try this at all, so might not work, but should
> give you the idea.
>
>>>
>>> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
>>> index b68c69d..4866144 100644
>>> --- a/hw/net/virtio-net.c
>>> +++ b/hw/net/virtio-net.c
>>> @@ -1164,6 +1164,7 @@ static ssize_t virtio_net_receive(NetClientState *nc,
>>> const uint8_t *buf, size_t
>>> offset = n->host_hdr_len;
>>> total += n->guest_hdr_len;
>>> guest_offset = n->guest_hdr_len;
>>> + continue;
>>> } else {
>>> guest_offset = 0;
>>> }
>>>
>>>
>>>
>>> here's one that should cap the 1st s/g to 100 bytes:
>>>
>>>
>>> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
>>> index b68c69d..7943004 100644
>>> --- a/hw/net/virtio-net.c
>>> +++ b/hw/net/virtio-net.c
>>> @@ -1164,6 +1164,7 @@ static ssize_t virtio_net_receive(NetClientState *nc,
>>> const uint8_t *buf, size_t
>>> offset = n->host_hdr_len;
>>> total += n->guest_hdr_len;
>>> guest_offset = n->guest_hdr_len;
>>> + sg.iov_len = MIN(sg.iov_len, 100);
>>> } else {
>>> guest_offset = 0;
>>> }
>>>
Here is the patch I went with, I'm using vhost=on:
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1777,7 +1777,8 @@ static int translate_desc(struct vhost_virtqueue
*vq, u64
_iov = iov + ret;
size = node->size - addr + node->start;
- _iov->iov_len = min((u64)len - s, size);
+ printk("%s: build 100 length headers!\n", __func__);
+ _iov->iov_len = min((u64)len - s, (u64)100);//size);
_iov->iov_base = (void __user *)(unsigned long)
(node->userspace_addr + addr - node->start);
s += size;
This seems to do the trick and with 100 I can use 'ping -s' to generate
as many bufs is needed up to MTU. The patch I have seems to be working
fine I'll let it run a bit and test it with some real traffic (not just
ping) then push out a v3 assuming I don't find any issues.
Thanks,
John
