From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ED843C433EF for ; Fri, 5 Nov 2021 23:29:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B9FE461056 for ; Fri, 5 Nov 2021 23:29:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232395AbhKEXcX (ORCPT ); Fri, 5 Nov 2021 19:32:23 -0400 Received: from mail.kernel.org ([198.145.29.99]:42572 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232329AbhKEXcP (ORCPT ); Fri, 5 Nov 2021 19:32:15 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 4633561037; Fri, 5 Nov 2021 23:29:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1636154975; bh=ItuVj4ZCBb/4t68SXxbU328vuz5etR5fJsUwxRKFs8U=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=GN5kjKXV5msCzLyxbKp2V+3kqUjL8Fp84chGjv23Jfkn4oHA9+66y+azvxCbYXVWj nKiKNTk83lG7s0AZNdWnlsqOnwokB1v3u/flTTLaqMYmDOcoGDaFU+9K9bBMJqcipW 5IODn/7P6pv9rFLUprRYZprAoheaVbnCRXUSgoR0VbuRasqom1sAOKbA1V8BY2BLhs jMEdemsBe/5cUSx22pEfGnJRfFxFLAAPaR181KzpY7AnGJTa+/dmM9/OWy8ObrhP8V gSop3/OV0lOLoI8IK9DmuK2bDJAXdyMBiGQDt+k+6YUN3R08lPt8oJiPWhUabUGNUV mBkzCmqF2kKSQ== Date: Fri, 5 Nov 2021 16:29:33 -0700 From: Jakub Kicinski To: Lorenzo Bianconi Cc: bpf@vger.kernel.org, netdev@vger.kernel.org, lorenzo.bianconi@redhat.com, davem@davemloft.net, ast@kernel.org, daniel@iogearbox.net, shayagr@amazon.com, john.fastabend@gmail.com, dsahern@kernel.org, brouer@redhat.com, echaudro@redhat.com, jasowang@redhat.com, alexander.duyck@gmail.com, saeed@kernel.org, maciej.fijalkowski@intel.com, magnus.karlsson@intel.com, tirthendu.sarkar@intel.com, toke@redhat.com Subject: Re: [PATCH v17 bpf-next 13/23] bpf: add multi-buffer support to xdp copy helpers Message-ID: <20211105162933.113ce3c5@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> In-Reply-To: <637cb9a21958e1a5026faba6255debf21d229d1d.1636044387.git.lorenzo@kernel.org> References: <637cb9a21958e1a5026faba6255debf21d229d1d.1636044387.git.lorenzo@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Thu, 4 Nov 2021 18:35:33 +0100 Lorenzo Bianconi wrote: > -static unsigned long bpf_xdp_copy(void *dst_buff, const void *src_buff, > +static unsigned long bpf_xdp_copy(void *dst_buff, const void *ctx, > unsigned long off, unsigned long len) > { > - memcpy(dst_buff, src_buff + off, len); > + unsigned long base_len, copy_len, frag_off_total; > + struct xdp_buff *xdp = (struct xdp_buff *)ctx; > + struct skb_shared_info *sinfo; > + int i; > + > + if (likely(!xdp_buff_is_mb(xdp))) { Would it be better to do if (xdp->data_end - xdp->data >= off + len) ? > + memcpy(dst_buff, xdp->data + off, len); > + return 0; > + } > + > + base_len = xdp->data_end - xdp->data; > + frag_off_total = base_len; > + sinfo = xdp_get_shared_info_from_buff(xdp); > + > + /* If we need to copy data from the base buffer do it */ > + if (off < base_len) { > + copy_len = min(len, base_len - off); > + memcpy(dst_buff, xdp->data + off, copy_len); > + > + off += copy_len; > + len -= copy_len; > + dst_buff += copy_len; > + } > + > + /* Copy any remaining data from the fragments */ > + for (i = 0; len && i < sinfo->nr_frags; i++) { > + skb_frag_t *frag = &sinfo->frags[i]; > + unsigned long frag_len, frag_off; > + > + frag_len = skb_frag_size(frag); > + frag_off = off - frag_off_total; > + if (frag_off < frag_len) { > + copy_len = min(len, frag_len - frag_off); > + memcpy(dst_buff, > + skb_frag_address(frag) + frag_off, copy_len); > + > + off += copy_len; > + len -= copy_len; > + dst_buff += copy_len; > + } > + frag_off_total += frag_len; > + } > + nit: can't help but feel that you can merge base copy and frag copy: sinfo = xdp_get_shared_info_from_buff(xdp); next_frag = &sinfo->frags[0]; end_frag = &sinfo->frags[sinfo->nr_frags]; ptr_off = 0; ptr_buf = xdp->data; ptr_len = xdp->data_end - xdp->data; while (true) { if (off < ptr_off + ptr_len) { copy_off = ptr_off - off; copy_len = min(len, ptr_len - copy_off); memcpy(dst_buff, ptr_buf + copy_off, copy_len); off += copy_len; len -= copy_len; dst_buff += copy_len; } if (!len || next_frag == end_frag) break; ptr_off += ptr_len; ptr_buf = skb_frag_address(next_frag); ptr_len = skb_frag_size(next_frag); next_frag++; } Up to you.