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nios2: ensure that memblock.current_limit is set when setting pfn limits

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On nios2, with CONFIG_FLATMEM set, the kernel relies on
memblock_get_current_limit() to determine the limits of mem_map, in
particular for max_low_pfn.
Unfortunately, memblock.current_limit is only default initialized to
MEMBLOCK_ALLOC_ANYWHERE at this point of the bootup, potentially leading
to situations where max_low_pfn can erroneously exceed the value of
max_pfn and, thus, the valid range of available DRAM.

This can in turn cause kernel-level paging failures, e.g.:

[   76.900000] Unable to handle kernel paging request at virtual address 20303000
[   76.900000] ea = c0080890, ra = c000462c, cause = 14
[   76.900000] Kernel panic - not syncing: Oops
[   76.900000] ---[ end Kernel panic - not syncing: Oops ]---

This patch fixes this by pre-calculating memblock.current_limit
based on the upper limits of the available memory ranges via
adjust_lowmem_bounds, a simplified version of the equivalent
implementation within the arm architecture.

Signed-off-by: Simon Schuster <schuster.simon@siemens-energy.com>
Signed-off-by: Andreas Oetken <andreas.oetken@siemens-energy.com>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>
This commit is contained in:
Simon Schuster
2025-08-21 12:37:07 +02:00
committed by Dinh Nguyen
parent e6d8afd2ca
commit a20b83cf45
1 changed files with 15 additions and 0 deletions
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15
arch/nios2/kernel/setup.c
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@@ -142,6 +142,20 @@ static void __init find_limits(unsigned long *min, unsigned long *max_low,
*max_high = PFN_DOWN(memblock_end_of_DRAM());
}
static void __init adjust_lowmem_bounds(void)
{
phys_addr_t block_start, block_end;
u64 i;
phys_addr_t memblock_limit = 0;
for_each_mem_range(i, &block_start, &block_end) {
if (block_end > memblock_limit)
memblock_limit = block_end;
}
memblock_set_current_limit(memblock_limit);
}
void __init setup_arch(char **cmdline_p)
{
console_verbose();
@@ -157,6 +171,7 @@ void __init setup_arch(char **cmdline_p)
/* Keep a copy of command line */
*cmdline_p = boot_command_line;
adjust_lowmem_bounds();
find_limits(&min_low_pfn, &max_low_pfn, &max_pfn);
memblock_reserve(__pa_symbol(_stext), _end - _stext);