On Tue, Jul 05, 2022 at 11:32:23AM -0600, Logan Gunthorpe wrote: > > > 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. Why would you want to do this through a sysfs interface? that feels horrid...
