Re: [PATCH v7 20/21] PCI/P2PDMA: Introduce pci_mmap_p2pmem()

Greg Kroah-Hartman
2022-07-05T17:22:07Z

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