On 2022-07-05 11:21, Greg Kroah-Hartman wrote: > 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? The P2PDMA code allocates and hands out struct pages to userspace that are backed with ZONE_DEVICE memory from a device's BAR. This is quite different from the existing binary files mentioned above which neither support struct pages nor allocation. Logan
