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 X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A1F7BC31E46 for ; Wed, 12 Jun 2019 10:26:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 81A36207E0 for ; Wed, 12 Jun 2019 10:26:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2407251AbfFLK0b (ORCPT ); Wed, 12 Jun 2019 06:26:31 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34516 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2405983AbfFLK0b (ORCPT ); Wed, 12 Jun 2019 06:26:31 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 3D4152F8BC3; Wed, 12 Jun 2019 10:26:26 +0000 (UTC) Received: from localhost (unknown [10.43.2.57]) by smtp.corp.redhat.com (Postfix) with ESMTP id D530917B92; Wed, 12 Jun 2019 10:26:16 +0000 (UTC) Date: Wed, 12 Jun 2019 12:25:05 +0200 From: Stanislaw Gruszka To: Lorenzo Bianconi Cc: Lorenzo Bianconi , nbd@nbd.name, kvalo@codeaurora.org, linux-wireless@vger.kernel.org Subject: Re: [PATCH v2 2/2] mt76: usb: do not always copy the first part of received frames Message-ID: <20190612102502.GB4431@redhat.com> References: <2ed0b595a12944a8cfea14e066bcc4fa24f0ba44.1559293385.git.lorenzo@kernel.org> <20190612091036.GB2965@redhat.com> <20190612095302.GD8107@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190612095302.GD8107@localhost.localdomain> User-Agent: Mutt/1.8.3 (2017-05-23) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Wed, 12 Jun 2019 10:26:31 +0000 (UTC) Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org On Wed, Jun 12, 2019 at 11:53:03AM +0200, Lorenzo Bianconi wrote: > > On Fri, May 31, 2019 at 11:38:23AM +0200, Lorenzo Bianconi wrote: > > [...] > > > > } > > > > > > urb->num_sgs = max_t(int, i, urb->num_sgs); > > > - urb->transfer_buffer_length = urb->num_sgs * q->buf_size, > > > + urb->transfer_buffer_length = urb->num_sgs * data_size; > > > sg_init_marker(urb->sg, urb->num_sgs); > > > > > > return i ? : -ENOMEM; > > > @@ -611,8 +611,12 @@ static int mt76u_alloc_rx(struct mt76_dev *dev) > > > if (!q->entry) > > > return -ENOMEM; > > > > > > - q->buf_size = dev->usb.sg_en ? MT_RX_BUF_SIZE : PAGE_SIZE; > > > + if (dev->usb.sg_en) > > > + q->buf_size = MT_BUF_WITH_OVERHEAD(MT_RX_BUF_SIZE); > > > > I strongly recommend to not doing this. While this should work > > in theory creating buffer with size of 2k + some bytes might > > trigger various bugs in dma mapping or other low level code. > > even in practice actually :) I wouldn't be sure about this. It's not common to have buffers of such size and crossing pages boundaries. It really can trigger nasty bugs on various IOMMU drivers. > but we can be more cautious since probably copying > the first 128B will not make any difference Not sure if I understand what you mean. > > And skb_shered_info is needed only in first buffer IIUC. > > > > Also this patch seems to make first patch unnecessary except for > > non sg_en case (in which I think rx AMSDU is broken anyway), > > so I would prefer just to apply first patch. > > I do not think rx AMSDU is broken for non sg_en case since the max rx value > allowed should be 3839 IIRC and we alloc one page in this case If that's the case we should be fine, but then I do not understand why we allocate 8*2k buffers for sg_en case, isn't that AP can sent AMSDU frame 16k big? Stanislaw