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    SubjectRe: [PATCH v3 1/4] Revert "Documentation/features: mark BATCHED_UNMAP_TLB_FLUSH doesn't apply to ARM64"
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    On 8/22/22 13:51, Yicong Yang wrote:
    > From: Barry Song <v-songbaohua@oppo.com>
    >
    > This reverts commit 6bfef171d0d74cb050112e0e49feb20bfddf7f42.
    >
    > I was wrong. Though ARM64 has hardware TLB flush, but it is not free
    > and it is still expensive.
    > We still have a good chance to enable batched and deferred TLB flush
    > on ARM64 for memory reclamation. A possible way is that we only queue
    > tlbi instructions in hardware's queue. When we have to broadcast TLB,
    > we broadcast it by dsb. We just need to get adapted the existing
    > BATCHED_UNMAP_TLB_FLUSH.
    >
    > Tested-by: Xin Hao <xhao@linux.alibaba.com>
    > Signed-off-by: Barry Song <v-songbaohua@oppo.com>
    > Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
    > ---
    > Documentation/features/arch-support.txt | 1 -
    > Documentation/features/vm/TLB/arch-support.txt | 2 +-
    > 2 files changed, 1 insertion(+), 2 deletions(-)
    >
    > diff --git a/Documentation/features/arch-support.txt b/Documentation/features/arch-support.txt
    > index 118ae031840b..d22a1095e661 100644
    > --- a/Documentation/features/arch-support.txt
    > +++ b/Documentation/features/arch-support.txt
    > @@ -8,5 +8,4 @@ The meaning of entries in the tables is:
    > | ok | # feature supported by the architecture
    > |TODO| # feature not yet supported by the architecture
    > | .. | # feature cannot be supported by the hardware
    > - | N/A| # feature doesn't apply to the architecture
    >
    > diff --git a/Documentation/features/vm/TLB/arch-support.txt b/Documentation/features/vm/TLB/arch-support.txt
    > index 039e4e91ada3..1c009312b9c1 100644
    > --- a/Documentation/features/vm/TLB/arch-support.txt
    > +++ b/Documentation/features/vm/TLB/arch-support.txt
    > @@ -9,7 +9,7 @@
    > | alpha: | TODO |
    > | arc: | TODO |
    > | arm: | TODO |
    > - | arm64: | N/A |
    > + | arm64: | TODO |
    > | csky: | TODO |
    > | hexagon: | TODO |
    > | ia64: | TODO |

    I believe this patch is not needed, which explicitly reverts an
    older commit. Instead when ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
    framework gets enabled on arm64, the same patch could just drop
    'NA' as possible values for arch support for a give feature in
    file Documentation/features/arch-support.txt.

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