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[207.54.116.67]) by mx.google.com with ESMTPS id c100si2321935itd.11.2019.01.29.12.44.24 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 29 Jan 2019 12:44:24 -0800 (PST) Received-SPF: pass (google.com: domain of logang@deltatee.com designates 207.54.116.67 as permitted sender) client-ip=207.54.116.67; Authentication-Results: mx.google.com; spf=pass (google.com: domain of logang@deltatee.com designates 207.54.116.67 as permitted sender) smtp.mailfrom=logang@deltatee.com Received: from guinness.priv.deltatee.com ([172.16.1.162]) by ale.deltatee.com with esmtp (Exim 4.89) (envelope-from ) id 1goaEu-0006kt-Rd; Tue, 29 Jan 2019 13:44:13 -0700 To: Greg Kroah-Hartman Cc: jglisse@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Rafael J . Wysocki" , Bjorn Helgaas , Christian Koenig , Felix Kuehling , Jason Gunthorpe , linux-pci@vger.kernel.org, dri-devel@lists.freedesktop.org, Christoph Hellwig , Marek Szyprowski , Robin Murphy , Joerg Roedel , iommu@lists.linux-foundation.org References: <20190129174728.6430-1-jglisse@redhat.com> <20190129174728.6430-2-jglisse@redhat.com> <20190129194426.GB32069@kroah.com> From: Logan Gunthorpe Message-ID: <8b4e0157-4eaf-c79a-28d0-7a266abe2207@deltatee.com> Date: Tue, 29 Jan 2019 13:44:09 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190129194426.GB32069@kroah.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-CA Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 172.16.1.162 X-SA-Exim-Rcpt-To: iommu@lists.linux-foundation.org, jroedel@suse.de, robin.murphy@arm.com, m.szyprowski@samsung.com, hch@lst.de, dri-devel@lists.freedesktop.org, linux-pci@vger.kernel.org, jgg@mellanox.com, Felix.Kuehling@amd.com, christian.koenig@amd.com, bhelgaas@google.com, rafael@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, jglisse@redhat.com, gregkh@linuxfoundation.org X-SA-Exim-Mail-From: logang@deltatee.com Subject: Re: [RFC PATCH 1/5] pci/p2p: add a function to test peer to peer capability X-SA-Exim-Version: 4.2.1 (built Tue, 02 Aug 2016 21:08:31 +0000) X-SA-Exim-Scanned: Yes (on ale.deltatee.com) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2019-01-29 12:44 p.m., Greg Kroah-Hartman wrote: > On Tue, Jan 29, 2019 at 11:24:09AM -0700, Logan Gunthorpe wrote: >> >> >> On 2019-01-29 10:47 a.m., jglisse@redhat.com wrote: >>> +bool pci_test_p2p(struct device *devA, struct device *devB) >>> +{ >>> + struct pci_dev *pciA, *pciB; >>> + bool ret; >>> + int tmp; >>> + >>> + /* >>> + * For now we only support PCIE peer to peer but other inter-connect >>> + * can be added. >>> + */ >>> + pciA = find_parent_pci_dev(devA); >>> + pciB = find_parent_pci_dev(devB); >>> + if (pciA == NULL || pciB == NULL) { >>> + ret = false; >>> + goto out; >>> + } >>> + >>> + tmp = upstream_bridge_distance(pciA, pciB, NULL); >>> + ret = tmp < 0 ? false : true; >>> + >>> +out: >>> + pci_dev_put(pciB); >>> + pci_dev_put(pciA); >>> + return false; >>> +} >>> +EXPORT_SYMBOL_GPL(pci_test_p2p); >> >> This function only ever returns false.... > > I guess it was nevr actually tested :( > > I feel really worried about passing random 'struct device' pointers into > the PCI layer. Are we _sure_ it can handle this properly? Yes, there are a couple of pci_p2pdma functions that take struct devices directly simply because it's way more convenient for the caller. That's what find_parent_pci_dev() takes care of (it returns false if the device is not a PCI device). Whether that's appropriate here is hard to say seeing we haven't seen any caller code. Logan