Re: [Xen-devel] [PATCH net] xen-netback: fix guest-receive-side array sizes

[David Miller <davem@xxxxxxxxxxxxx>]

From: Paul Durrant <paul.durrant@xxxxxxxxxx>
Date: Mon, 23 Dec 2013 09:27:17 +0000

> The sizes chosen for the metadata and grant_copy_op arrays on the guest
> receive size are wrong;
> 
> - The meta array is needlessly twice the ring size, when we only ever
>   consume a single array element per RX ring slot
> - The grant_copy_op array is way too small. It's sized based on a bogus
>   assumption: that at most two copy ops will be used per ring slot. This
>   may have been true at some point in the past but it's clear from looking
>   at start_new_rx_buffer() that a new ring slot is only consumed if a frag
>   would overflow the current slot (plus some other conditions) so the actual
>   limit is MAX_SKB_FRAGS grant_copy_ops per ring slot.
> 
> This patch fixes those two sizing issues and, because grant_copy_ops grows
> so much, it pulls it out into a separate chunk of vmalloc()ed memory.
> 
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>

Applied, thanks.

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