6.15-stable review patch. If anyone has any objections, please let me know.
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From: Alexander Gordeev agordeev@linux.ibm.com
[ Upstream commit 56f4cfab1c93b14da422cdcd23898eb008033696 ]
The value of high_memory variable is set by set_high_memory() function to a value returned by memblock_end_of_DRAM(). The latter function returns by default the upper bound of the last online memory block, not the upper bound of the directly mapped memory region. As result, in case the end of memory happens to be offline, high_memory variable is set to a value that is short on the last offline memory blocks size:
RANGE SIZE STATE REMOVABLE BLOCK 0x0000000000000000-0x000000ffffffffff 1T online yes 0-511 0x0000010000000000-0x0000011fffffffff 128G offline 512-575
Memory block size: 2G Total online memory: 1T Total offline memory: 128G
crash> p/x vm_layout $1 = { kaslr_offset = 0x3453e918000, kaslr_offset_phys = 0xa534218000, identity_base = 0x0, identity_size = 0x12000000000 } crash> p/x high_memory $2 = 0x10000000000
In the past the value of high_memory was derived from max_low_pfn, which in turn was derived from the identity_size. Since identity_size accommodates the whole memory size - including tailing offline blocks, the offlined blocks did not impose any problem. But since commit e120d1bc12da ("arch, mm: set high_memory in free_area_init()") the value of high_memory is derived from the last memblock online region, and that is where the problem comes from.
The value of high_memory is used by several drivers and by external tools (e.g. crash tool aborts while loading a dump).
Similarily to ARM, use the override path provided by set_high_memory() function and set the value of high_memory at the end of the identity mapping early. That forces set_high_memory() to leave in high_memory the correct value, even when the end of available memory is offline.
Fixes: e120d1bc12da ("arch, mm: set high_memory in free_area_init()") Tested-by: Mikhail Zaslonko zaslonko@linux.ibm.com Reviewed-by: Heiko Carstens hca@linux.ibm.com Reviewed-by: Gerald Schaefer gerald.schaefer@linux.ibm.com Signed-off-by: Alexander Gordeev agordeev@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/kernel/setup.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c index f244c5560e7f..5c9789804120 100644 --- a/arch/s390/kernel/setup.c +++ b/arch/s390/kernel/setup.c @@ -719,6 +719,11 @@ static void __init memblock_add_physmem_info(void) memblock_set_node(0, ULONG_MAX, &memblock.memory, 0); }
+static void __init setup_high_memory(void) +{ + high_memory = __va(ident_map_size); +} + /* * Reserve memory used for lowcore. */ @@ -951,6 +956,7 @@ void __init setup_arch(char **cmdline_p)
free_physmem_info(); setup_memory_end(); + setup_high_memory(); memblock_dump_all(); setup_memory();