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| author | Arnd Bergmann <arnd@arndb.de> | 2025-02-26 22:37:09 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2025-02-27 11:21:53 +0100 |
| commit | bbeb69ce301323e84f1677484eb8e4cd8fb1f9f8 (patch) | |
| tree | 580c8053fb356f4d4f5a6282873baf5ac0644bfc /Documentation/admin-guide/kdump | |
| parent | f388f60ca9041a95c9b3f157d316ed7c8f297e44 (diff) | |
| download | lwn-bbeb69ce301323e84f1677484eb8e4cd8fb1f9f8.tar.gz lwn-bbeb69ce301323e84f1677484eb8e4cd8fb1f9f8.zip | |
x86/mm: Remove CONFIG_HIGHMEM64G support
HIGHMEM64G support was added in linux-2.3.25 to support (then)
high-end Pentium Pro and Pentium III Xeon servers with more than 4GB of
addressing, NUMA and PCI-X slots started appearing.
I have found no evidence of this ever being used in regular dual-socket
servers or consumer devices, all the users seem obsolete these days,
even by i386 standards:
- Support for NUMA servers (NUMA-Q, IBM x440, unisys) was already
removed ten years ago.
- 4+ socket non-NUMA servers based on Intel 450GX/450NX, HP F8 and
ServerWorks ServerSet/GrandChampion could theoretically still work
with 8GB, but these were exceptionally rare even 20 years ago and
would have usually been equipped with than the maximum amount of
RAM.
- Some SKUs of the Celeron D from 2004 had 64-bit mode fused off but
could still work in a Socket 775 mainboard designed for the later
Core 2 Duo and 8GB. Apparently most BIOSes at the time only allowed
64-bit CPUs.
- The rare Xeon LV "Sossaman" came on a few motherboards with
registered DDR2 memory support up to 16GB.
- In the early days of x86-64 hardware, there was sometimes the need
to run a 32-bit kernel to work around bugs in the hardware drivers,
or in the syscall emulation for 32-bit userspace. This likely still
works but there should never be a need for this any more.
PAE mode is still required to get access to the 'NX' bit on Atom
'Pentium M' and 'Core Duo' CPUs.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250226213714.4040853-6-arnd@kernel.org
Diffstat (limited to 'Documentation/admin-guide/kdump')
| -rw-r--r-- | Documentation/admin-guide/kdump/kdump.rst | 4 |
1 files changed, 0 insertions, 4 deletions
diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst index 5376890adbeb..1f7f14c6e184 100644 --- a/Documentation/admin-guide/kdump/kdump.rst +++ b/Documentation/admin-guide/kdump/kdump.rst @@ -180,10 +180,6 @@ Dump-capture kernel config options (Arch Dependent, i386 and x86_64) 1) On i386, enable high memory support under "Processor type and features":: - CONFIG_HIGHMEM64G=y - - or:: - CONFIG_HIGHMEM4G 2) With CONFIG_SMP=y, usually nr_cpus=1 need specified on the kernel |