Messages in this thread | | | Date | Wed, 12 Mar 2014 19:47:34 +0800 | From | Liu hua <> | Subject | [ARM]Fixmap mapping region is not enough for system of 14+ CPUs. |
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Hi Russell, Will or Nicolas,
(In this mail, we only discuss ARM 32-bit linux.)
As we know, the region (0xfff00000-0xfffdffff) is reserved as fixmap mapping region.
The function "kmap_atomic" maps highmem pages to this region referring to CPUID and per-cpu variable "__kmap_atomic_idx" via
idx = type + KM_TYPE_NR * smp_processor_id(); vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
Size of region used by one cpu is 0x10000 (KM_TYPE_NR << PAGE_SHIFT). And the total size of the fixmap mapping region is 0xe0000. (only support 14 CPUs).
So in a system of more than 14 CPUs, this region is not large enough. should we change the memory layout on ARM Linux to support 14+ cpu system ? Or can we do anything else to support that ?
Thanks,
Liu Hua
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