Re: [PATCH v1 6/6] arm64: tlb: Set the TTL field in flush_tlb_range

Peter Zijlstra
2020-04-20T12:12:04Z

On Fri, Apr 03, 2020 at 05:00:48PM +0800, Zhenyu Ye wrote:
> This patch uses the cleared_* in struct mmu_gather to set the
> TTL field in flush_tlb_range().
>
> Signed-off-by: Zhenyu Ye <yezhenyu2@huawei.com>
> ---
> arch/arm64/include/asm/tlb.h | 26 +++++++++++++++++++++++++-
> arch/arm64/include/asm/tlbflush.h | 14 ++++++++------
> 2 files changed, 33 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h
> index b76df828e6b7..d5ab72eccff4 100644
> --- a/arch/arm64/include/asm/tlb.h
> +++ b/arch/arm64/include/asm/tlb.h
> @@ -21,11 +21,34 @@ static void tlb_flush(struct mmu_gather *tlb);
>
> #include <asm-generic/tlb.h>
>
> +/*
> + * get the tlbi levels in arm64. Default value is 0 if more than one
> + * of cleared_* is set or neither is set.
> + * Arm64 doesn't support p4ds now.
> + */
> +static inline int tlb_get_level(struct mmu_gather *tlb)
> +{
> + int sum = tlb->cleared_ptes + tlb->cleared_pmds +
> + tlb->cleared_puds + tlb->cleared_p4ds;
> +
> + if (sum != 1)
> + return 0;
> + else if (tlb->cleared_ptes)
> + return 3;
> + else if (tlb->cleared_pmds)
> + return 2;
> + else if (tlb->cleared_puds)
> + return 1;
> +
> + return 0;
> +}

That's some mighty wonky code. Please look at the generated asm.