Re: [PATCH v1 8/9] mm/mmu_gather: add tlb_remove_tlb_entries()

[Ryan Roberts]

On 29/01/2024 14:32, David Hildenbrand wrote:
> Let's add a helper that lets us batch-process multiple consecutive PTEs.
> 
> Note that the loop will get optimized out on all architectures except on
> powerpc. We have to add an early define of __tlb_remove_tlb_entry() on
> ppc to make the compiler happy (and avoid making tlb_remove_tlb_entries() a
> macro).
> 
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>

Reviewed-by: Ryan Roberts <ryan.roberts@xxxxxxx>

> ---
>  arch/powerpc/include/asm/tlb.h |  2 ++
>  include/asm-generic/tlb.h      | 20 ++++++++++++++++++++
>  2 files changed, 22 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/tlb.h b/arch/powerpc/include/asm/tlb.h
> index b3de6102a907..1ca7d4c4b90d 100644
> --- a/arch/powerpc/include/asm/tlb.h
> +++ b/arch/powerpc/include/asm/tlb.h
> @@ -19,6 +19,8 @@
>  
>  #include <linux/pagemap.h>
>  
> +static inline void __tlb_remove_tlb_entry(struct mmu_gather *tlb, pte_t *ptep,
> +					  unsigned long address);
>  #define __tlb_remove_tlb_entry	__tlb_remove_tlb_entry
>  
>  #define tlb_flush tlb_flush
> diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
> index 428c3f93addc..bd00dd238b79 100644
> --- a/include/asm-generic/tlb.h
> +++ b/include/asm-generic/tlb.h
> @@ -616,6 +616,26 @@ static inline void tlb_flush_p4d_range(struct mmu_gather *tlb,
>  		__tlb_remove_tlb_entry(tlb, ptep, address);	\
>  	} while (0)
>  
> +/**
> + * tlb_remove_tlb_entries - remember unmapping of multiple consecutive ptes for
> + *			    later tlb invalidation.
> + *
> + * Similar to tlb_remove_tlb_entry(), but remember unmapping of multiple
> + * consecutive ptes instead of only a single one.
> + */
> +static inline void tlb_remove_tlb_entries(struct mmu_gather *tlb,
> +		pte_t *ptep, unsigned int nr, unsigned long address)
> +{
> +	tlb_flush_pte_range(tlb, address, PAGE_SIZE * nr);
> +	for (;;) {
> +		__tlb_remove_tlb_entry(tlb, ptep, address);
> +		if (--nr == 0)
> +			break;
> +		ptep++;
> +		address += PAGE_SIZE;
> +	}
> +}
> +
>  #define tlb_remove_huge_tlb_entry(h, tlb, ptep, address)	\
>  	do {							\
>  		unsigned long _sz = huge_page_size(h);		\