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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
26 lines
654 B
Plaintext
26 lines
654 B
Plaintext
# global x86 required specific stuff
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CONFIG_64BIT=y
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# These enable us to allow some of the
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# not so generic stuff below
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CONFIG_HYPERVISOR_GUEST=y
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CONFIG_PCI=y
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CONFIG_PCI_MSI=y
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CONFIG_X86_MCE=y
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CONFIG_ACPI_PROCESSOR=y
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CONFIG_CPU_FREQ=y
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# x86 xen specific config options
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CONFIG_XEN_PVH=y
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CONFIG_XEN_SAVE_RESTORE=y
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# CONFIG_XEN_DEBUG_FS is not set
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CONFIG_XEN_MCE_LOG=y
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CONFIG_XEN_ACPI_PROCESSOR=m
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# x86 specific backend drivers
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CONFIG_XEN_PCIDEV_BACKEND=m
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# x86 specific frontend drivers
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CONFIG_XEN_PCIDEV_FRONTEND=m
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# depends on MEMORY_HOTPLUG, arm64 doesn't enable this yet,
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# move to generic config if it ever does.
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CONFIG_XEN_BALLOON_MEMORY_HOTPLUG=y
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