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 0E01FC4332F for ; Thu, 28 Oct 2021 07:56:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E98D161152 for ; Thu, 28 Oct 2021 07:56:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229877AbhJ1H7P (ORCPT ); Thu, 28 Oct 2021 03:59:15 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:25321 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229626AbhJ1H7O (ORCPT ); Thu, 28 Oct 2021 03:59:14 -0400 Received: from dggeme758-chm.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4HfySj5lDbzbhNc; Thu, 28 Oct 2021 15:52:05 +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 15.1.2308.15; Thu, 28 Oct 2021 15:56:45 +0800 Subject: Re: [PATCH V10 6/8] PCI/P2PDMA: Add a 10-Bit Tag check in P2PDMA To: Bjorn Helgaas References: <20211027212048.GA252528@bhelgaas> CC: , , , , , , , , From: Dongdong Liu Message-ID: <5773efae-8fb6-bd63-0486-dfcd14d3c8ae@huawei.com> Date: Thu, 28 Oct 2021 15:56:45 +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: <20211027212048.GA252528@bhelgaas> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.103.235] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) 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 2021/10/28 5:20, Bjorn Helgaas wrote: > On Sat, Oct 09, 2021 at 06:49:36PM +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. > > Shouldn't this also take into account Extended Tags (8 bits)? I think > the only tag size guaranteed to be supported is 5 bits. As all PCIe completers are required to support 8-bit tags, seems no need to take into account Extended Tags. > >> Before that happens, the kernel should emit a warning. > > The warning is nice, but the critical thing is that the P2PDMA mapping > should fail so we don't attempt DMA in this situation. I guess that's > sort of what you're saying with "ensure that a device ... doesn't > interact with a device ..." Yes, that is. > >> "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. >> >> Signed-off-by: Dongdong Liu >> Reviewed-by: Logan Gunthorpe >> --- >> drivers/pci/p2pdma.c | 48 ++++++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 48 insertions(+) >> >> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c >> index 50cdde3e9a8b..804e390f4c22 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 +411,50 @@ static unsigned long map_types_idx(struct pci_dev *client) >> (client->bus->number << 8) | client->devfn; >> } >> >> +static bool pci_10bit_tags_unsupported(struct pci_dev *a, >> + struct pci_dev *b, >> + bool verbose) >> +{ >> + bool req; >> + bool comp; >> + u16 ctl; >> + const char *str = "10bit_tag"; >> + >> + if (a->is_virtfn) { >> +#ifdef CONFIG_PCI_IOV >> + req = !!(a->physfn->sriov->ctrl & >> + PCI_SRIOV_CTRL_VF_10BIT_TAG_REQ_EN); >> +#endif >> + } else { >> + pcie_capability_read_word(a, PCI_EXP_DEVCTL2, &ctl); >> + req = !!(ctl & PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN); >> + } >> + >> + comp = !!(b->devcap2 & PCI_EXP_DEVCAP2_10BIT_TAG_COMP); >> + /* 10-bit tags not enabled on requester */ >> + if (!req) >> + return false; >> + >> + /* Completer can handle anything */ >> + if (comp) >> + return false; >> + >> + if (!verbose) >> + return true; >> + >> + pci_warn(a, "cannot be used for peer-to-peer DMA as 10-Bit Tag Requester enable is set for this device, but peer device (%s) does not support the 10-Bit Tag Completer\n", >> + pci_name(b)); >> + >> + if (a->is_virtfn) >> + str = "sriov_vf_10bit_tag_ctl"; >> + >> + pci_warn(a, "to disable 10-Bit Tag Requester for this device, echo 0 > /sys/bus/pci/devices/%s/%s\n", >> + pci_name(a), str); >> + >> + return true; >> +} >> + >> /* >> * Calculate the P2PDMA mapping type and distance between two PCI devices. >> * >> @@ -532,6 +577,9 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client, >> map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; >> } >> done: >> + if (pci_10bit_tags_unsupported(client, provider, verbose)) >> + map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; >> + >> rcu_read_lock(); >> p2pdma = rcu_dereference(provider->p2pdma); >> if (p2pdma) >> -- >> 2.22.0 >> > . >