From: John Hubbard <jhubb...@nvidia.com>
The HMM_MIRROR option in Kconfig is a little underdocumented and
mysterious, and leaves people wondering whether to enable it.
Add text explaining just a little bit more about HMM, and also
mention which hardware would benefit from having HMM_MIRROR
enabled.
Suggested-by: Pavel Machek <pa...@ucw.cz>
Cc: Balbir Singh <bsinghar...@gmail.com>
Cc: Dan Williams <dan.j.willi...@intel.com>
Cc: Jason Gunthorpe <j...@ziepe.ca>
Cc: Jerome Glisse <jgli...@redhat.com>
Cc: Christoph Hellwig <h...@infradead.org>
Signed-off-by: John Hubbard <jhubb...@nvidia.com>
---
Hi Pavel and all, does this help? I've tried to capture the key missing bits
of documentation, but still keep it small, for Kconfig.
thanks,
John Hubbard
NVIDIA
mm/Kconfig | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)
diff --git a/mm/Kconfig b/mm/Kconfig
index 56cec636a1fc..2fcb92e7f696 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -681,11 +681,18 @@ config HMM_MIRROR
depends on MMU && 64BIT
select MMU_NOTIFIER
help
- Select HMM_MIRROR if you want to mirror range of the CPU page table
of a
- process into a device page table. Here, mirror means "keep
synchronized".
- Prerequisites: the device must provide the ability to write-protect
its
- page tables (at PAGE_SIZE granularity), and must be able to recover
from
- the resulting potential page faults.
+ This is Heterogeneous Memory Management (HMM) process address space
+ mirroring.
+
+ HMM_MIRROR provides a way to mirror ranges of the CPU page tables
+ of a process into a device page table. Here, mirror means "keep
+ synchronized". Prerequisites: the device must provide the ability
+ to write-protect its page tables (at PAGE_SIZE granularity), and
+ must be able to recover from the resulting potential page faults.
+
+ Select HMM_MIRROR if you have hardware that meets the above
+ description. An early, partial list of such hardware is:
+ an NVIDIA GPU >= Pascal, Mellanox IB >= mlx5, or an AMD GPU.
config DEVICE_PRIVATE
bool "Unaddressable device memory (GPU memory, ...)"
--
2.22.0
