Re: [PATCH v7 06/12] arm64: tlb: Refactor the core flush algorithm of __flush_tlb_range

[Marc Zyngier]

On Sat, 22 Jul 2023 03:22:45 +0100,
Raghavendra Rao Ananta <rananta@xxxxxxxxxx> wrote:
> 
> Currently, the core TLB flush functionality of __flush_tlb_range()
> hardcodes vae1is (and variants) for the flush operation. In the
> upcoming patches, the KVM code reuses this core algorithm with
> ipas2e1is for range based TLB invalidations based on the IPA.
> Hence, extract the core flush functionality of __flush_tlb_range()
> into its own macro that accepts an 'op' argument to pass any
> TLBI operation, such that other callers (KVM) can benefit.
> 
> No functional changes intended.
> 
> Signed-off-by: Raghavendra Rao Ananta <rananta@xxxxxxxxxx>
> Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> Reviewed-by: Gavin Shan <gshan@xxxxxxxxxx>
> Reviewed-by: Shaoqin Huang <shahuang@xxxxxxxxxx>
> ---
>  arch/arm64/include/asm/tlbflush.h | 109 +++++++++++++++---------------
>  1 file changed, 56 insertions(+), 53 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
> index 412a3b9a3c25..f7fafba25add 100644
> --- a/arch/arm64/include/asm/tlbflush.h
> +++ b/arch/arm64/include/asm/tlbflush.h
> @@ -278,14 +278,62 @@ static inline void flush_tlb_page(struct vm_area_struct *vma,
>   */
>  #define MAX_TLBI_OPS	PTRS_PER_PTE
>  
> +/* When the CPU does not support TLB range operations, flush the TLB
> + * entries one by one at the granularity of 'stride'. If the TLB
> + * range ops are supported, then:

Comment format (the original was correct).

> + *
> + * 1. If 'pages' is odd, flush the first page through non-range
> + *    operations;
> + *
> + * 2. For remaining pages: the minimum range granularity is decided
> + *    by 'scale', so multiple range TLBI operations may be required.
> + *    Start from scale = 0, flush the corresponding number of pages
> + *    ((num+1)*2^(5*scale+1) starting from 'addr'), then increase it
> + *    until no pages left.
> + *
> + * Note that certain ranges can be represented by either num = 31 and
> + * scale or num = 0 and scale + 1. The loop below favours the latter
> + * since num is limited to 30 by the __TLBI_RANGE_NUM() macro.
> + */
> +#define __flush_tlb_range_op(op, start, pages, stride,			\
> +				asid, tlb_level, tlbi_user)		\

If you make this a common macro, please document the parameters, and
what the constraints are. For example, what does tlbi_user mean for an
IPA invalidation?

	M.

-- 
Without deviation from the norm, progress is not possible.