This driver exposes p2pmem to userspace without taking appropriate safety measures to ensure it is used correctly. If you do certain things with the pointers obtained by mmapping the /dev/p2pmemX exposed by this driver bad things will probably happen. Consider yourself warned.

This is a standlone PCIe driver that ties into the p2pmem framework. It can be used for any PCIe end-point devices that have registered one or more PCIe BAR(s) with the p2pdma framework (e.g. NVM Express CMBs).

To build the module as a .ko for manually installation run:

make KDIR=/path/to/kernel/source

Note the resultant kernel module is called p2pmem_pci.ko. To install the module in the current kernel's module tree run:

make install

Note that for this to work you either need to have module signing set up or turned off on your machine. Also this code will only work for >= 4.20.x kernels. Please look for the largest tag that is less than or equal to your kernel version and use that tag.

Often you don't want to compile against the kernel installed on your host so you can use the instructions here that describe how to prepare a kernel tree for out-of-tree module compilation. The following process seems to work well (in the top level kernel source folder):

1. make distclean.
2. Setup your .config (don't forget you will need p2pdma enabled).
3. make modules_prepare.

You can now go back to your p2pmem-pci repository and run the make command as noted previously. Note you might get the following warning when you build the module.

WARNING: Symbol version dump ./Module.symvers
is missing; modules will have no dependencies and modversions.

This behaviour is expected.

Once this module has been inserted you should see a /dev/p2pmemX for each of the p2pmem regions in your system. You can then use mmap() to obtain virtual address pointers backed by memory on the PCIe BAR(s) associated with /dev/p2pmemX. You can then pass these pointers into library functions like write() and read() as long as you use O_DIRECT.

An example of how to use /dev/p2pmemX is via p2pmem-test which also has more information on setting up p2pdma enabled kernels and a p2pdma capable system.