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arm64: mm: Modify calculation of VMEMMAP_SIZE 

In a later patch we will need to have a slightly larger VMEMMAP region
to accommodate boot time selection between 48/52-bit kernel VAs.

This patch modifies the formula for computing VMEMMAP_SIZE to depend
explicitly on the PAGE_OFFSET and start of kernel addressable memory.
(This allows for a slightly larger direct linear map in future).

Signed-off-by: Steve Capper <steve.capper@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Steve Capper 2019-08-07 16:55:21 +01:00 committed by Will Deacon
parent c8b6d2ccf9
commit ce3aaed873
1 changed files with 8 additions and 1 deletions
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9
arch/arm64/include/asm/memory.h
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@ -26,8 +26,15 @@
/*
* VMEMMAP_SIZE - allows the whole linear region to be covered by
* a struct page array
*
* If we are configured with a 52-bit kernel VA then our VMEMMAP_SIZE
* neads to cover the memory region from the beginning of the 52-bit
* PAGE_OFFSET all the way to VA_START for 48-bit. This allows us to
* keep a constant PAGE_OFFSET and "fallback" to using the higher end
* of the VMEMMAP where 52-bit support is not available in hardware.
*/
#define VMEMMAP_SIZE (UL(1) << (VA_BITS - PAGE_SHIFT - 1 + STRUCT_PAGE_MAX_SHIFT))
#define VMEMMAP_SIZE ((_VA_START(VA_BITS_MIN) - PAGE_OFFSET) \
>> (PAGE_SHIFT - STRUCT_PAGE_MAX_SHIFT))
/*
* PAGE_OFFSET - the virtual address of the start of the linear map (top