powerpc/40x: Limit allocable DRAM during early mapping (5907630f) · Commits · 戴 / test

If the size of DRAM is not an exact power of two, we may not have covered DRAM in its entirety with large 16 and 4 MiB pages. If that is the case, we can get non-recoverable page faults when doing the final PTE mappings for the non-large page PTEs. Consequently, we restrict the top end of DRAM currently allocable by updating '__initial_memory_limit_addr' so that calls to the LMB to allocate PTEs for "tail" coverage with normal-sized pages (or other reasons) do not attempt to allocate outside the allowed range. Signed-off-by:

Grant Erickson <gerickson@nuovations.com> Signed-off-by:

Josh Boyer <jwboyer@linux.vnet.ibm.com>

arch/powerpc/mm/40x_mmu.c

+14 −2

Original line number	Diff line number	Diff line
		@@ -93,7 +93,7 @@ void __init MMU_init_hw(void)

		unsigned long __init mmu_mapin_ram(void)
		{
		unsigned long v, s;
		unsigned long v, s, mapped;
		phys_addr_t p;

		v = KERNELBASE;
		@@ -130,5 +130,17 @@ unsigned long __init mmu_mapin_ram(void)
		s -= LARGE_PAGE_SIZE_4M;
		}

		return total_lowmem - s;
		mapped = total_lowmem - s;

		/* If the size of RAM is not an exact power of two, we may not
		* have covered RAM in its entirety with 16 and 4 MiB
		* pages. Consequently, restrict the top end of RAM currently
		* allocable so that calls to the LMB to allocate PTEs for "tail"
		* coverage with normal-sized pages (or other reasons) do not
		* attempt to allocate outside the allowed range.
		*/

		__initial_memory_limit_addr = memstart_addr + mapped;

		return mapped;
		}

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