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

[ Upstream commit a20b83cf45be2057f3d073506779e52c7fa17f94 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/nios2/kernel/setup.c b/arch/nios2/kernel/setup.c
index 40bc8fb75e0b50fbb6fcc026169537e908d12390..e2fc4b59d93ea9a7eccd3d4e421e38e94e310def 100644 (file)
--- a/arch/nios2/kernel/setup.c
+++ b/arch/nios2/kernel/setup.c
@@ -147,6 +147,20 @@ 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();
@@ -160,6 +174,7 @@ 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);
        max_mapnr = max_low_pfn;