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

Ryan Roberts
2024-01-30T09:33:25Z

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@redhat.com>

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

> ---
> 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); \