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Date:   Tue, 29 Jan 2019 20:44:26 +0100
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Logan Gunthorpe <logang@deltatee.com>
Cc:     jglisse@redhat.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        "Rafael J . Wysocki" <rafael@kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Christian Koenig <christian.koenig@amd.com>,
        Felix Kuehling <Felix.Kuehling@amd.com>,
        Jason Gunthorpe <jgg@mellanox.com>, linux-pci@vger.kernel.org,
        dri-devel@lists.freedesktop.org, Christoph Hellwig <hch@lst.de>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Joerg Roedel <jroedel@suse.de>,
        iommu@lists.linux-foundation.org
Subject: Re: [RFC PATCH 1/5] pci/p2p: add a function to test peer to peer
 capability
Message-ID: <20190129194426.GB32069@kroah.com>
References: <20190129174728.6430-1-jglisse@redhat.com>
 <20190129174728.6430-2-jglisse@redhat.com>
 <f66ba584-9c4a-f6cd-c647-9b32a93be807@deltatee.com>
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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?

thanks,

greg k-h