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commit 353d7a84c214f184d5a6b62acdec8b4424159b7c upstream. When KFENCE is enabled, total system memory is mapped at page level granularity. But in radix MMU mode, ~3GB additional memory is needed to map 100GB of system memory at page level granularity when compared to using 2MB direct mapping.This is not desired considering KFENCE is designed to be enabled in production kernels [1]. Mapping only the memory allocated for KFENCE pool at page granularity is sufficient to enable KFENCE support. So, allocate __kfence_pool during bootup and map it at page granularity instead of mapping all system memory at page granularity. Without patch: # cat /proc/meminfo MemTotal: 101201920 kB With patch: # cat /proc/meminfo MemTotal: 104483904 kB Note that enabling KFENCE at runtime is disabled for radix MMU for now, as it depends on the ability to split page table mappings and such APIs are not currently implemented for radix MMU. All kfence_test.c testcases passed with this patch. [1] https://lore.kernel.org/all/20201103175841.3495947-2-elver@google.com/ Signed-off-by: Hari Bathini <hbathini@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/20240701130021.578240-1-hbathini@linux.ibm.com Cc: Aboorva Devarajan <aboorvad@linux.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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 Restructured Text 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.