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Date:   Tue, 5 Jul 2022 19:21:58 +0200
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Christoph Hellwig <hch@lst.de>
Cc:     Logan Gunthorpe <logang@deltatee.com>,
        Jason Gunthorpe <jgg@ziepe.ca>, linux-kernel@vger.kernel.org,
        linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
        linux-pci@vger.kernel.org, linux-mm@kvack.org,
        iommu@lists.linux-foundation.org,
        Stephen Bates <sbates@raithlin.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Christian =?iso-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>,
        John Hubbard <jhubbard@nvidia.com>,
        Don Dutile <ddutile@redhat.com>,
        Matthew Wilcox <willy@infradead.org>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        Minturn Dave B <dave.b.minturn@intel.com>,
        Jason Ekstrand <jason@jlekstrand.net>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Xiong Jianxin <jianxin.xiong@intel.com>,
        Bjorn Helgaas <helgaas@kernel.org>,
        Ira Weiny <ira.weiny@intel.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Martin Oliveira <martin.oliveira@eideticom.com>,
        Chaitanya Kulkarni <ckulkarnilinux@gmail.com>,
        Ralph Campbell <rcampbell@nvidia.com>,
        Bjorn Helgaas <bhelgaas@google.com>
Subject: Re: [PATCH v7 20/21] PCI/P2PDMA: Introduce pci_mmap_p2pmem()
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On Tue, Jul 05, 2022 at 06:50:39PM +0200, Christoph Hellwig wrote:
> [note for the newcomers, this is about allowing mmap()ing the PCIe
> P2P memory from the generic PCI P2P code through sysfs, and more
> importantly how to revoke it on device removal]

We allow mmap on PCIe config space today, right?  Why is this different
from what pci_create_legacy_files() does today?

> On Tue, Jul 05, 2022 at 10:44:49AM -0600, Logan Gunthorpe wrote:
> > We might be able to. I'm not sure. I'll have to figure out how to find
> > that inode from the p2pdma code. I haven't found an obvious interface to
> > do that.
> 
> I think the right way to approach this would be a new sysfs API
> that internally calls unmap_mapping_range internally instead of
> exposing the inode. I suspect that might actually be the right thing
> to do for iomem_inode as well.

Why do we need something new and how is this any different from the PCI
binary files I mention above?  We have supported PCI hotplug for a very
long time, do the current PCI binary sysfs files not work properly with
mmap and removing a device?

thanks,

greg k-h