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=-16.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 11040C432BE for ; Mon, 9 Aug 2021 17:31:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E6C3760F56 for ; Mon, 9 Aug 2021 17:31:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234337AbhHIRbg (ORCPT ); Mon, 9 Aug 2021 13:31:36 -0400 Received: from mail.kernel.org ([198.145.29.99]:38996 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233996AbhHIRbf (ORCPT ); Mon, 9 Aug 2021 13:31:35 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id CE141604DC; Mon, 9 Aug 2021 17:31:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1628530275; bh=eDy1pEzRt6RUJc3M+OdmFDgeBpFyrnusEt6fYQvnavU=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=B0Wi30G8/HhJIylJTtEL4v1GoqNPI0mOQgVd8xULg+NA5dfVLS5RUhnsbTSycKp3v +EbkHHiTStAXkfj6/q19uu6IrSUOK3lARbC+PhKsjLZlg2l7aZ7VMZWCeKHYY5H2Ye +h1lmR9iwsyGwjDTD+vqmEzXkWSUc/WElw7QQZKoPhFj1vSFfMlRfr/1W2QOxEfiKH Z0ufkojNh3NEPeyjm71P08YzGnoHm4QnonbSlDdqANHzVyVyjkQR6QQh6GyvMFwgzu t+Rl6ewTdRJ15Z97FQ5dKB9gjzoCSTPzo4FPyySFozRG4rtO6nBTA2h+E5qGlPKQvn rNyzEIwhLG5wg== Date: Mon, 9 Aug 2021 12:31:13 -0500 From: Bjorn Helgaas To: Dongdong Liu Cc: hch@infradead.org, kw@linux.com, logang@deltatee.com, leon@kernel.org, linux-pci@vger.kernel.org, rajur@chelsio.com, hverkuil-cisco@xs4all.nl, linux-media@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH V7 9/9] PCI/P2PDMA: Add a 10-Bit Tag check in P2PDMA Message-ID: <20210809173113.GA2166744@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <11f98331-cc39-ee37-85f7-185fdd1ccea5@huawei.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sat, Aug 07, 2021 at 03:11:34PM +0800, Dongdong Liu wrote: > > On 2021/8/6 2:12, Bjorn Helgaas wrote: > > On Wed, Aug 04, 2021 at 09:47:08PM +0800, Dongdong Liu wrote: > > > Add a 10-Bit Tag check in the P2PDMA code to ensure that a device with > > > 10-Bit Tag Requester doesn't interact with a device that does not > > > support 10-BIT Tag Completer. Before that happens, the kernel should > > > emit a warning. "echo 0 > /sys/bus/pci/devices/.../10bit_tag" to > > > disable 10-BIT Tag Requester for PF device. > > > "echo 0 > /sys/bus/pci/devices/.../sriov_vf_10bit_tag_ctl" to disable > > > 10-BIT Tag Requester for VF device. > > > > s/10-BIT/10-Bit/ several times. > Will fix. > > > > Add blank lines between paragraphs. > Will fix. > > > > > Signed-off-by: Dongdong Liu > > > --- > > > drivers/pci/p2pdma.c | 40 ++++++++++++++++++++++++++++++++++++++++ > > > 1 file changed, 40 insertions(+) > > > > > > diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c > > > index 50cdde3..948f2be 100644 > > > --- a/drivers/pci/p2pdma.c > > > +++ b/drivers/pci/p2pdma.c > > > @@ -19,6 +19,7 @@ > > > #include > > > #include > > > #include > > > +#include "pci.h" > > > > > > enum pci_p2pdma_map_type { > > > PCI_P2PDMA_MAP_UNKNOWN = 0, > > > @@ -410,6 +411,41 @@ static unsigned long map_types_idx(struct pci_dev *client) > > > (client->bus->number << 8) | client->devfn; > > > } > > > > > > +static bool check_10bit_tags_vaild(struct pci_dev *a, struct pci_dev *b, > > > > s/vaild/valid/ > > > > Or maybe s/valid/safe/ or s/valid/supported/, since "valid" isn't > > quite the right word here. We want to know whether the source is > > enabled to generate 10-bit tags, and if so, whether the destination > > can handle them. > > > > "if (check_10bit_tags_valid())" does not make sense because > > "check_10bit_tags_valid()" is not a question with a yes/no answer. > > > > "10bit_tags_valid()" *might* be, because "if (10bit_tags_valid())" > > makes sense. But I don't think you can start with a digit. > > > > Or maybe you want to invert the sense, e.g., > > "10bit_tags_unsupported()", since that avoids negation at the caller: > > > > if (10bit_tags_unsupported(a, b) || > > 10bit_tags_unsupported(b, a)) > > map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; > Good suggestion. add a pci_ prefix. > > if (pci_10bit_tags_unsupported(a, b) || > pci_10bit_tags_unsupported(b, a)) > map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; This treats both directions as equally important. I don't know P2PDMA very well, but that doesn't seem like it would necessarily be the case. I would think a common case would be device A doing DMA to B, but B *not* doing DMA to A. So can you tell which direction you're setting up here, and can you take advantage of any asymmetry, e.g., by enabling 10-bit tags in the direction that supports it even if the other direction does not?