ABI: sysfs-bus-pci: add documentation for p2pmem allocate

Add documentation for the p2pmem/allocate binary file which allows
for allocating p2pmem buffers in userspace for passing to drivers
that support them. (Currently only O_DIRECT to NVMe devices.)

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20221021174116.7200-10-logang@deltatee.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
index 840727f..ecf4755 100644 (file)
--- a/Documentation/ABI/testing/sysfs-bus-pci
+++ b/Documentation/ABI/testing/sysfs-bus-pci
@@ -407,6 +407,16 @@ Description:
                file contains a '1' if the memory has been published for
                use outside the driver that owns the device.
 
+What:          /sys/bus/pci/devices/.../p2pmem/allocate
+Date:          August 2022
+Contact:       Logan Gunthorpe <logang@deltatee.com>
+Description:
+               This file allows mapping p2pmem into userspace. For each
+               mmap() call on this file, the kernel will allocate a chunk
+               of Peer-to-Peer memory for use in Peer-to-Peer transactions.
+               This memory can be used in O_DIRECT calls to NVMe backed
+               files for Peer-to-Peer copies.
+
 What:          /sys/bus/pci/devices/.../link/clkpm
                /sys/bus/pci/devices/.../link/l0s_aspm
                /sys/bus/pci/devices/.../link/l1_aspm