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 C8C3AC433F5 for ; Wed, 27 Oct 2021 21:21:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B44E7610CA for ; Wed, 27 Oct 2021 21:21:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236867AbhJ0VYS (ORCPT ); Wed, 27 Oct 2021 17:24:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:35664 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232208AbhJ0VXP (ORCPT ); Wed, 27 Oct 2021 17:23:15 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 4D111610CA; Wed, 27 Oct 2021 21:20:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1635369649; bh=XAKQElgr6BBu1UxLggaDKytR7eU4feqnPzmw0g25Rh0=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=p0b4YLUwvJPjelhXK6tuNGSLxPc8W57wzTHLdwcnMUmPB94v3hsvXslXLq1TZ7GY3 sL93c85du1ZkOYvv6Pe8m//9lhA+RCJvKPQ3Uxy4IpiUrRzmmHS2TjXc+bDuZhbHC1 l+E73WotWsbVG9NLfon08np6Kd/XgVf0Jxca7lyT4yX6vB73LFYEef0IfwG2arUu8/ 99lPcmeJ/rIFzzRSmhPjxtiZo5dpdJB8a4yC6OHadP/Fj4Qj6F80bnWXW+gPhJdbdy kbLLEj07eEaOlMSzDYq1FQHtoTNtzXOYOJc/bLD1mWl8TMf9oIuR/1QaiRsDmFW7pE HwI4EGZ6WMvrg== Date: Wed, 27 Oct 2021 16:20:48 -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 V10 6/8] PCI/P2PDMA: Add a 10-Bit Tag check in P2PDMA Message-ID: <20211027212048.GA252528@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211009104938.48225-7-liudongdong3@huawei.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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. > 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 ..." > "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 >