arm64: tlb: Use the TLBI RANGE feature in arm64

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Add __TLBI_VADDR_RANGE macro and rewrite __flush_tlb_range().

When cpu supports TLBI feature, the minimum range granularity is
decided by 'scale', so we can not flush all pages by one instruction
in some cases.

For example, when the pages = 0xe81a, let's start 'scale' from
maximum, and find right 'num' for each 'scale':

1. scale = 3, we can flush no pages because the minimum range is
   2^(5*3 + 1) = 0x10000.
2. scale = 2, the minimum range is 2^(5*2 + 1) = 0x800, we can
   flush 0xe800 pages this time, the num = 0xe800/0x800 - 1 = 0x1c.
   Remaining pages is 0x1a;
3. scale = 1, the minimum range is 2^(5*1 + 1) = 0x40, no page
   can be flushed.
4. scale = 0, we flush the remaining 0x1a pages, the num =
   0x1a/0x2 - 1 = 0xd.

However, in most scenarios, the pages = 1 when flush_tlb_range() is
called. Start from scale = 3 or other proper value (such as scale =
ilog2(pages)), will incur extra overhead.
So increase 'scale' from 0 to maximum, the flush order is exactly
opposite to the example.

Signed-off-by: Zhenyu Ye <yezhenyu2@huawei.com>
Link: https://lore.kernel.org/r/20200715071945.897-4-yezhenyu2@huawei.com
[catalin.marinas@arm.com: removed unnecessary masks in __TLBI_VADDR_RANGE]
[catalin.marinas@arm.com: __TLB_RANGE_NUM subtracts 1]
[catalin.marinas@arm.com: minor adjustments to the comments]
[catalin.marinas@arm.com: introduce system_supports_tlb_range()]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

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This commit is contained in:

Zhenyu Ye 2020-07-15 15:19:45 +08:00 • committed by Catalin Marinas

parent 7c78f67e9b

commit d1d3aa98b1

2 changed files with 131 additions and 29 deletions

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6

arch/arm64/include/asm/cpufeature.h

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156

arch/arm64/include/asm/tlbflush.h

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