Re: [PATCH bpf-next v6 07/12] net/mlx5e: Allow XSK frames smaller than a page

[Jonathan Lemon]

On 26 Aug 2019, at 19:25, Kevin Laatz wrote:

> From: Maxim Mikityanskiy <maxi...@mellanox.com>
>
> Relax the requirements to the XSK frame size to allow it to be smaller
> than a page and even not a power of two. The current implementation can
> work in this mode, both with Striding RQ and without it.
>
> The code that checks `mtu + headroom <= XSK frame size` is modified
> accordingly. Any frame size between 2048 and PAGE_SIZE is accepted.
>
> Functions that worked with pages only now work with XSK frames, even if
> their size is different from PAGE_SIZE.
>
> With XSK queues, regardless of the frame size, Striding RQ uses the
> stride size of PAGE_SIZE, and UMR MTTs are posted using starting
> addresses of frames, but PAGE_SIZE as page size. MTU guarantees that no
> packet data will overlap with other frames. UMR MTT size is made equal
> to the stride size of the RQ, because UMEM frames may come in random
> order, and we need to handle them one by one. PAGE_SIZE is just a power
> of two that is bigger than any allowed XSK frame size, and also it
> doesn't require making additional changes to the code.
>
> Signed-off-by: Maxim Mikityanskiy <maxi...@mellanox.com>
> Reviewed-by: Saeed Mahameed <sae...@mellanox.com>
Acked-by: Jonathan Lemon <jonathan.le...@gmail.com>