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Date: Mon, 7 Sep 2020 19:22:39 -0600 From: David Ahern <dsahern@...il.com> To: Jesper Dangaard Brouer <brouer@...hat.com> Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>, Lorenzo Bianconi <lorenzo@...nel.org>, netdev@...r.kernel.org, bpf@...r.kernel.org, davem@...emloft.net, lorenzo.bianconi@...hat.com, echaudro@...hat.com, sameehj@...zon.com, kuba@...nel.org, john.fastabend@...il.com, daniel@...earbox.net, ast@...nel.org, shayagr@...zon.com, David Ahern <dsahern@...nel.org>, Ilias Apalodimas <ilias.apalodimas@...aro.org> Subject: Re: [PATCH v2 net-next 1/9] xdp: introduce mb in xdp_buff/xdp_frame On 9/7/20 12:02 PM, Jesper Dangaard Brouer wrote: > >> ok, is there any alignment requirement? can frame_sz be number of 32-bit >> words? I believe bit shifts are cheap. > > No that is not possible, because some drivers and generic-XDP have a > fully dynamic frame_sz. > frame_sz represents allocated memory right? What is the real range that needs to be supported for frame_sz? Surely there is some upper limit, and I thought it was 64kB. Allocated memory will not be on an odd number, so fair to assume at a minimum it is a multiple of 2. correct? At a minimum we should be able to shift frame_sz by 1 which now covers 64kB in a u16.
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