v.maffione_gmail.com added a comment.
Yes, but I think the story is more complex than that. Guests can publish
single-descriptor chains or multi-descriptor chains, depending on feature
negotiation and driver implementation. With mergeable buffers enabled, or TSO
features disabled, guests will normally submit single-descriptor chains
(because it makes sense), but this is not mandatory. With TSO enabled and
mergeable buffers disabled, guests will normally pass in multi-descriptor
chains, each one describing 64K or 32K buffers.
It makes sense to add more vq methods to handle the mergeable rx bufs case,
but think they should be moved to usr.sbin/bhyve/virtio.c, so that they can be
reused.
INLINE COMMENTS
> pci_virtio_net.c:525
> +
> + if (ndesc < minavail)
> + return (0);
why this check? if there are not enough descriptors to cover 'len' bytes the
function will return 0 anyway.
> pci_virtio_net.c:526
> + if (ndesc < minavail)
> + return (0);
> +
You are mixing declarations and code here. Is it allowed?
> pci_virtio_net.c:670
>
> - /* Interrupt if needed, including for NOTIFY_ON_EMPTY. */
> + vq_inc_used_idx_and_last_avail(vq, used);
> vq_endchains(vq, 1);
I think you should call vq_inc_used_idx_and_last_avail() after each packet,
otherwise you are introducing artificial latency. As a side effect, this allows
you to remove the "start" argument ("used" local variable) and the used local
variable.
> pci_virtio_net.c:673
> +
> + return;
> }
why this return?
CHANGES SINCE LAST ACTION
https://reviews.freebsd.org/D20276/new/
REVISION DETAIL
https://reviews.freebsd.org/D20276
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To: aleksandr.fedorov_itglobal.com, #bhyve, jhb, rgrimes, krion,
v.maffione_gmail.com
Cc: mizhka_gmail.com, novel, olevole_olevole.ru, freebsd-virtualization-list,
evgueni.gavrilov_itglobal.com, bcran
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