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| H A D | tun.c | diff 885291761dba2bfe04df4c0f7bb75e4c920ab82e Wed Jul 17 21:55:15 CDT 2013 Jason Wang <jasowang@redhat.com> tuntap: do not zerocopy if iov needs more pages than MAX_SKB_FRAGS
We try to linearize part of the skb when the number of iov is greater than
MAX_SKB_FRAGS. This is not enough since each single vector may occupy more than
one pages, so zerocopy_sg_fromiovec() may still fail and may break the guest
network.
Solve this problem by calculate the pages needed for iov before trying to do
zerocopy and switch to use copy instead of zerocopy if it needs more than
MAX_SKB_FRAGS.
This is done through introducing a new helper to count the pages for iov, and
call uarg->callback() manually when switching from zerocopy to copy to notify
vhost.
We can do further optimization on top.
The bug were introduced from commit 0690899b4d4501b3505be069b9a687e68ccbe15b
(tun: experimental zero copy tx support)
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff 3dd5c3308e8b671e8e8882ba972f51cefbe9fd0d Wed Jul 10 00:43:27 CDT 2013 Jason Wang <jasowang@redhat.com> tuntap: correctly linearize skb when zerocopy is used
Userspace may produce vectors greater than MAX_SKB_FRAGS. When we try to
linearize parts of the skb to let the rest of iov to be fit in
the frags, we need count copylen into linear when calling tun_alloc_skb()
instead of partly counting it into data_len. Since this breaks
zerocopy_sg_from_iovec() since its inner counter assumes nr_frags should
be zero at beginning. This cause nr_frags to be increased wrongly without
setting the correct frags.
This bug were introduced from 0690899b4d4501b3505be069b9a687e68ccbe15b
(tun: experimental zero copy tx support)
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff 0690899b4d4501b3505be069b9a687e68ccbe15b Fri Jul 20 04:23:23 CDT 2012 Michael S. Tsirkin <mst@redhat.com> tun: experimental zero copy tx support
Let vhost-net utilize zero copy tx when used with tun.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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