[BUG] vhost-net: Enabling experimental_zcopytx always crashes the host on 5.10, worked fine on 5.4

[BUG] vhost-net: Enabling experimental_zcopytx always crashes the host on 5.10, worked fine on 5.4

[Roman Mamedov]

Hello,

I am upgrading my VM host from 5.4.126 to 5.10.46.
The host started crashing almost instantly after boot.

The issue is traced down to:

If the vhost-net module is loaded with "experimental_zcopytx=1", as soon as a
Windows KVM guest boots up and starts doing even a light network load
(watching YouTube), the entire host crashes with a backtrace pointing to
skb_segment, parts of which I was able to capture.

This is reproducible 100% of the time, got 3 identical crashes before getting
a capture and then flipping the parameter to 0. With it set to 0 the issue
goes away.

Reported at [1], not sure if that was the best place for the report, thought
maybe posting here as well won't hurt.

Thanks

[1] https://bugzilla.kernel.org/show_bug.cgi?id=213563

-- 
With respect,
Roman