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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 07929C4320E for ; Tue, 10 Aug 2021 12:31:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E35A160FC4 for ; Tue, 10 Aug 2021 12:31:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240574AbhHJMb4 (ORCPT ); Tue, 10 Aug 2021 08:31:56 -0400 Received: from szxga01-in.huawei.com ([45.249.212.187]:17001 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238518AbhHJMbz (ORCPT ); Tue, 10 Aug 2021 08:31:55 -0400 Received: from dggeme758-chm.china.huawei.com (unknown [172.30.72.53]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4GkXKN6PHnzb0VN; Tue, 10 Aug 2021 20:27:52 +0800 (CST) Received: from [10.67.103.235] (10.67.103.235) by dggeme758-chm.china.huawei.com (10.3.19.104) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Tue, 10 Aug 2021 20:31:31 +0800 Subject: Re: [PATCH V7 9/9] PCI/P2PDMA: Add a 10-Bit Tag check in P2PDMA To: Bjorn Helgaas References: <20210809173113.GA2166744@bjorn-Precision-5520> CC: , , , , , , , , From: Dongdong Liu Message-ID: Date: Tue, 10 Aug 2021 20:31:30 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: <20210809173113.GA2166744@bjorn-Precision-5520> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.103.235] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggeme758-chm.china.huawei.com (10.3.19.104) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2021/8/10 1:31, Bjorn Helgaas wrote: > 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? Documentation/driver-api/pci/p2pdma.rst * Provider - A driver which provides or publishes P2P resources like memory or doorbell registers to other drivers. * Client - A driver which makes use of a resource by setting up a DMA transaction to or from it. So we may just check as below. if (10bit_tags_unsupported(client, provider, verbose) map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; @Logan What's your opinion? Thanks, Dongdong > . >