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Yishai Hadas 6dbd547ada IB/mlx5: Reduce IMR KSM size when 5-level paging is enabled 
Enabling 5-level paging (LA57) increases TASK_SIZE on x86_64 from 2^47
to 2^56. This affects implicit ODP, which uses TASK_SIZE to calculate
the number of IMR KSM entries.

As a result, the number of entries and the memory usage for KSM mkeys
increase drastically:

- With 2^47 TASK_SIZE: 0x20000 entries (~2MB)
- With 2^56 TASK_SIZE: 0x4000000 entries (~1GB)

This issue could happen previously on systems with LA57 manually
enabled, but now commit 7212b58d6d ("x86/mm/64: Make 5-level paging
support unconditional") enables LA57 by default on all supported
systems. This makes the issue impact widespread.

To mitigate this, increase the size each MTT entry maps from 1GB to 16GB
when 5-level paging is enabled. This reduces the number of KSM entries
and lowers the memory usage on LA57 systems from 1GB to 64MB per IMR.

As now 'mlx5_imr_mtt_size' is larger than 32 bits, we move to use u64
instead of int as part of populate_klm() to prevent overflow of the
'step' variable.

In addition, as populate_klm() actually handles KSM and not KLM, as it's
used only by implicit ODP, we renamed its signature and the internal
structures accordingly while dropping the byte_count handling which is
not relevant in KSM. The page size in KSM is fixed for all the entries
and come from the log_page_size of the mkey.

Note:
On platforms where the calculated value for 'mlx5_imr_ksm_page_shift' is
higher than the max firmware cap to be changed over UMR, or that the
calculated value for 'log_va_pages' is higher than what we may expect,
the implicit ODP cap will be simply turned off.

Co-developed-by: Or Har-Toov <ohartoov@nvidia.com>
Signed-off-by: Or Har-Toov <ohartoov@nvidia.com>
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Reviewed-by: Michael Guralnik <michaelgur@nvidia.com>
Signed-off-by: Edward Srouji <edwards@nvidia.com>
Link: https://patch.msgid.link/20251120-reduce-ksm-v1-1-6864bfc814dc@kernel.org
Signed-off-by: Leon Romanovsky <leon@kernel.org>
2025-11-24 02:58:30 -05:00
arch Kbuild fixes for 6.18 #1 2025-10-11 15:47:12 -07:00
block block-6.18-20251009 2025-10-10 10:37:13 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto This push contains the following changes: 2025-10-10 08:56:16 -07:00
Documentation RTC for 6.18 2025-10-11 11:56:47 -07:00
drivers IB/mlx5: Reduce IMR KSM size when 5-level paging is enabled 2025-11-24 02:58:30 -05:00
fs - Avoid -Wflex-array-member-not-at-end warnings 2025-10-10 14:06:02 -07:00
include RDMA/cm: Correct typedef and bad line warnings 2025-11-12 04:39:12 -05:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring/zcrx: increment fallback loop src offset 2025-10-08 07:26:14 -06:00
ipc namespace-6.18-rc1 2025-09-29 11:20:29 -07:00
kernel tracing fixes for v6.18: 2025-10-11 16:06:04 -07:00
lib lib/test_kho: use kho_preserve_vmalloc instead of storing addresses in fdt 2025-10-07 13:48:56 -07:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm slab hotfix for 6.18-rc1 2025-10-11 10:40:24 -07:00
net bpf-fixes 2025-10-11 10:31:38 -07:00
rust 7 hotfixes. All 7 are cc:stable and all 7 are for MM. 2025-10-11 10:14:55 -07:00
samples Char/Misc/IIO/Binder changes for 6.18-rc1 2025-10-04 16:26:32 -07:00
scripts Kbuild fixes for 6.18 #1 2025-10-11 15:47:12 -07:00
security integrity-v6.18 2025-10-05 10:48:33 -07:00
sound sound fixes for 6.18-rc1 2025-10-10 09:55:19 -07:00
tools - Remove a bunch of asm implementing condition flags testing in KVM's 2025-10-11 11:19:16 -07:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt hyperv-next for v6.18 2025-10-07 08:40:15 -07:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap MAINTAINERS, .mailmap: update Umang's email address 2025-10-07 13:48:55 -07:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS USB/Thunderbolt changes for 6.18-rc1 2025-10-04 16:07:08 -07:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS RDMA/bng_re: Add Auxiliary interface 2025-11-24 02:58:29 -05:00
Makefile Linux 6.18-rc1 2025-10-12 13:42:36 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.