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,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 4C53CC41537 for ; Sat, 7 Aug 2021 07:02:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0DEBE61205 for ; Sat, 7 Aug 2021 07:02:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231442AbhHGHCR (ORCPT ); Sat, 7 Aug 2021 03:02:17 -0400 Received: from szxga08-in.huawei.com ([45.249.212.255]:13243 "EHLO szxga08-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230297AbhHGHCQ (ORCPT ); Sat, 7 Aug 2021 03:02:16 -0400 Received: from dggeme758-chm.china.huawei.com (unknown [172.30.72.54]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4GhYDW1f4Bz1CR0v; Sat, 7 Aug 2021 15:01:47 +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; Sat, 7 Aug 2021 15:01:56 +0800 Subject: Re: [PATCH V7 7/9] PCI/sysfs: Add a 10-Bit Tag sysfs file To: Bjorn Helgaas References: <20210805153135.GA1757362@bjorn-Precision-5520> CC: , , , , , , , , From: Dongdong Liu Message-ID: <68b85d0a-37d2-f83d-99ba-cd3936af4005@huawei.com> Date: Sat, 7 Aug 2021 15:01:56 +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: <20210805153135.GA1757362@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: dggems704-chm.china.huawei.com (10.3.19.181) 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 2021/8/5 23:31, Bjorn Helgaas wrote: > On Thu, Aug 05, 2021 at 04:37:39PM +0800, Dongdong Liu wrote: >> >> >> On 2021/8/5 7:49, Bjorn Helgaas wrote: >>> On Wed, Aug 04, 2021 at 09:47:06PM +0800, Dongdong Liu wrote: >>>> PCIe spec 5.0 r1.0 section 2.2.6.2 says that if an Endpoint supports >>>> sending Requests to other Endpoints (as opposed to host memory), the >>>> Endpoint must not send 10-Bit Tag Requests to another given Endpoint >>>> unless an implementation-specific mechanism determines that the Endpoint >>>> supports 10-Bit Tag Completer capability. Add a 10bit_tag sysfs file, >>>> write 0 to disable 10-Bit Tag Requester when the driver does not bind >>>> the device if the peer device does not support the 10-Bit Tag Completer. >>>> This will make P2P traffic safe. the 10bit_tag file content indicate >>>> current 10-Bit Tag Requester Enable status. >>>> >>>> Signed-off-by: Dongdong Liu >>>> --- >>>> Documentation/ABI/testing/sysfs-bus-pci | 16 +++++++- >>>> drivers/pci/pci-sysfs.c | 69 +++++++++++++++++++++++++++++++++ >>>> 2 files changed, 84 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci >>>> index 793cbb7..0e0c97d 100644 >>>> --- a/Documentation/ABI/testing/sysfs-bus-pci >>>> +++ b/Documentation/ABI/testing/sysfs-bus-pci >>>> @@ -139,7 +139,7 @@ Description: >>>> binary file containing the Vital Product Data for the >>>> device. It should follow the VPD format defined in >>>> PCI Specification 2.1 or 2.2, but users should consider >>>> - that some devices may have incorrectly formatted data. >>>> + that some devices may have incorrectly formatted data. >>>> If the underlying VPD has a writable section then the >>>> corresponding section of this file will be writable. >>>> >>>> @@ -407,3 +407,17 @@ Description: >>>> >>>> The file is writable if the PF is bound to a driver that >>>> implements ->sriov_set_msix_vec_count(). >>>> + >>>> +What: /sys/bus/pci/devices/.../10bit_tag >>>> +Date: August 2021 >>>> +Contact: Dongdong Liu >>>> +Description: >>>> + If a PCI device support 10-Bit Tag Requester, will create the >>>> + 10bit_tag sysfs file. The file is readable, the value >>>> + indicate current 10-Bit Tag Requester Enable. >>>> + 1 - enabled, 0 - disabled. >>>> + >>>> + The file is also writeable, the value only accept by write 0 >>>> + to disable 10-Bit Tag Requester when the driver does not bind >>>> + the deivce. The typical use case is for p2pdma when the peer >>>> + device does not support 10-BIT Tag Completer. > >>>> +static ssize_t pci_10bit_tag_store(struct device *dev, >>>> + struct device_attribute *attr, >>>> + const char *buf, size_t count) >>>> +{ >>>> + struct pci_dev *pdev = to_pci_dev(dev); >>>> + bool enable; >>>> + >>>> + if (kstrtobool(buf, &enable) < 0) >>>> + return -EINVAL; >>>> + >>>> + if (enable != false ) >>>> + return -EINVAL; >>> >>> Is this the same as "if (enable)"? >> Yes, Will fix. > > I actually don't like the one-way nature of this. When the hierarchy > supports 10-bit tags, we automatically enable them during enumeration. > > Then we provide this sysfs file, but it can only *disable* 10-bit > tags. There's no way to re-enable them except by rebooting (or using > setpci, I guess). > > Why can't we allow *enabling* them here if they're supported in this > hierarchy? Yes, we can also provide this sysfs to enable 10-bit tag for EP devices when the hierarchy supports 10-bit tags. I do not want to provide sysfs to enable/disable 10-bit tag for RP devices as I can not tell current if the the Function has outstanding Non-Posted Requests, may need to unbind all the EP drivers under the RP, and current seems no scenario need to do this. This will make things more complex. Thanks, Dongdong > >>>> + if (pdev->driver) >>>> + return -EBUSY; >>>> + >>>> + pcie_capability_clear_word(pdev, PCI_EXP_DEVCTL2, >>>> + PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN); >>>> + pci_info(pdev, "disabled 10-Bit Tag Requester\n"); >>>> + >>>> + return count; >>>> +} > . >