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Subject[PATCH v6 0/4] Adjust the padding size for KASLR
Date
From: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>

The system sometimes crashes while memory hot-adding on KASLR
enabled system. The crash happens because the regions pointed by
kaslr_regions[].base are overwritten by the hot-added memory.

It happens because of the padding size for kaslr_regions[].base isn't
enough for the system whose physical memory layout has huge space for
memory hotplug. kaslr_regions[].base points "actual installed
memory size + padding" or higher address. So, if the "actual + padding"
is lower address than the maximum memory address, which means the memory
address reachable by memory hot-add, kaslr_regions[].base is destroyed by
the overwritten.

address
^
|------- maximum memory address (Hotplug)
| ^
|------- kaslr_regions[0].base | Hotadd-able region
| ^ |
| | padding |
| V V
|------- actual memory address (Installed on boot)
|

Fix it by getting the maximum memory address from SRAT and store
the value in boot_param, then set the padding size while KASLR
initializing if the default padding size isn't enough.

Changelog:
v6: - Add documents to top of calc_direct_mapping_size() to
explain why the size of direct mapping area is configured
as boot_params.max_addr (0004 patch).
- Add Acked-by from Baoquan (0004 patch).

Masayoshi Mizuma (4):
x86/boot: Wrap up the SRAT traversing code into subtable_parse()
x86/boot: Add max_addr field in struct boot_params
x86/boot: Get the max address from SRAT
x86/mm/KASLR: Adjust the padding size for the direct mapping.

Documentation/x86/zero-page.rst | 4 ++
arch/x86/boot/compressed/acpi.c | 42 +++++++++++++++---
arch/x86/include/uapi/asm/bootparam.h | 2 +-
arch/x86/mm/kaslr.c | 63 ++++++++++++++++++++-------
4 files changed, 88 insertions(+), 23 deletions(-)

--
2.20.1

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