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Fri, 20 Mar 2020 12:22:07 -0700 (PDT) Date: Fri, 20 Mar 2020 15:22:01 -0400 From: Andy Gospodarek To: Jesper Dangaard Brouer Cc: sameehj@amazon.com, Michael Chan , Andy Gospodarek , netdev@vger.kernel.org, bpf@vger.kernel.org, zorik@amazon.com, akiyano@amazon.com, gtzalik@amazon.com, Toke =?iso-8859-1?Q?H=F8iland-J=F8rgensen?= , Daniel Borkmann , Alexei Starovoitov , John Fastabend , Alexander Duyck , Jeff Kirsher , David Ahern , Willem de Bruijn , Ilias Apalodimas , Lorenzo Bianconi Subject: Re: [PATCH RFC v1 03/15] bnxt: add XDP frame size to driver Message-ID: <20200320192201.GA21532@C02YVCJELVCG.greyhouse.net> References: <158446612466.702578.2795159620575737080.stgit@firesoul> <158446616289.702578.7889111879119296431.stgit@firesoul> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <158446616289.702578.7889111879119296431.stgit@firesoul> Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Tue, Mar 17, 2020 at 06:29:22PM +0100, Jesper Dangaard Brouer wrote: > This driver uses full PAGE_SIZE pages when XDP is enabled. > > Cc: Michael Chan > Cc: Andy Gospodarek > Signed-off-by: Jesper Dangaard Brouer > --- > drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c > index c6f6f2033880..5e3b4a3b69ea 100644 > --- a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c > +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c > @@ -138,6 +138,7 @@ bool bnxt_rx_xdp(struct bnxt *bp, struct bnxt_rx_ring_info *rxr, u16 cons, > xdp_set_data_meta_invalid(&xdp); > xdp.data_end = *data_ptr + *len; > xdp.rxq = &rxr->xdp_rxq; > + xdp.frame_sz = PAGE_SIZE; /* BNXT_RX_PAGE_MODE(bp) when XDP enabled */ So if we want this to be the true size that the packet inside the the DMA buffer could grow to, I _think_ this would need to be: xdp.frame_sz = PAGE_SIZE - XDP_PACKET_HEADROOM; but I also noted that in patch 8 of the series that there is a check against data_end - data_hard_start, so functionally your original patch appears to be correct. If the intent was just to capture the size of the [DMA] buffer available for the datagram, maybe calling this new field 'buf_sz' or similar would be nice as it does not convey anything about the on-wire size like 'frame_sz' does. > orig_data = xdp.data; > > rcu_read_lock(); > >