On Wed, Sep 26, 2018 at 01:36:28PM +0200, Peter Zijlstra wrote:
> Provide a generic tlb_flush() implementation that relies on
> flush_tlb_range(). This is a little awkward because flush_tlb_range()
> assumes a VMA for range invalidation, but we no longer have one.
>
> Audit of all flush_tlb_range() implementations shows only vma->vm_mm
> and vma->vm_flags are used, and of the latter only VM_EXEC (I-TLB
> invalidates) and VM_HUGETLB (large TLB invalidate) are used.
>
> Therefore, track VM_EXEC and VM_HUGETLB in two more bits, and create a
> 'fake' VMA.
>
> This allows architectures that have a reasonably efficient
> flush_tlb_range() to not require any additional effort.
>
> Cc: Nick Piggin <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: "Aneesh Kumar K.V" <[email protected]>
> Cc: Will Deacon <[email protected]>
> Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
> ---
> arch/arm64/include/asm/tlb.h | 1
> arch/powerpc/include/asm/tlb.h | 1
> arch/riscv/include/asm/tlb.h | 1
> arch/x86/include/asm/tlb.h | 1
> include/asm-generic/tlb.h | 80
> +++++++++++++++++++++++++++++++++++------
> 5 files changed, 74 insertions(+), 10 deletions(-)
>
> --- a/arch/arm64/include/asm/tlb.h
> +++ b/arch/arm64/include/asm/tlb.h
> @@ -27,6 +27,7 @@ static inline void __tlb_remove_table(vo
> free_page_and_swap_cache((struct page *)_table);
> }
>
> +#define tlb_flush tlb_flush
> static void tlb_flush(struct mmu_gather *tlb);
>
> #include <asm-generic/tlb.h>
> --- a/arch/powerpc/include/asm/tlb.h
> +++ b/arch/powerpc/include/asm/tlb.h
> @@ -28,6 +28,7 @@
> #define tlb_end_vma(tlb, vma) do { } while (0)
> #define __tlb_remove_tlb_entry __tlb_remove_tlb_entry
>
> +#define tlb_flush tlb_flush
> extern void tlb_flush(struct mmu_gather *tlb);
>
> /* Get the generic bits... */
> --- a/arch/riscv/include/asm/tlb.h
> +++ b/arch/riscv/include/asm/tlb.h
> @@ -18,6 +18,7 @@ struct mmu_gather;
>
> static void tlb_flush(struct mmu_gather *tlb);
>
> +#define tlb_flush tlb_flush
> #include <asm-generic/tlb.h>
>
> static inline void tlb_flush(struct mmu_gather *tlb)
> --- a/arch/x86/include/asm/tlb.h
> +++ b/arch/x86/include/asm/tlb.h
> @@ -6,6 +6,7 @@
> #define tlb_end_vma(tlb, vma) do { } while (0)
> #define __tlb_remove_tlb_entry(tlb, ptep, address) do { } while (0)
>
> +#define tlb_flush tlb_flush
> static inline void tlb_flush(struct mmu_gather *tlb);
>
> #include <asm-generic/tlb.h>
> --- a/include/asm-generic/tlb.h
> +++ b/include/asm-generic/tlb.h
> @@ -241,6 +241,12 @@ struct mmu_gather {
> unsigned int cleared_puds : 1;
> unsigned int cleared_p4ds : 1;
>
> + /*
> + * tracks VM_EXEC | VM_HUGETLB in tlb_start_vma
> + */
> + unsigned int vma_exec : 1;
> + unsigned int vma_huge : 1;
> +
> unsigned int batch_count;
>
> struct mmu_gather_batch *active;
> @@ -282,7 +288,35 @@ static inline void __tlb_reset_range(str
> tlb->cleared_pmds = 0;
> tlb->cleared_puds = 0;
> tlb->cleared_p4ds = 0;
> + /*
> + * Do not reset mmu_gather::vma_* fields here, we do not
> + * call into tlb_start_vma() again to set them if there is an
> + * intermediate flush.
> + */
> +}
> +
> +#ifndef tlb_flush
> +
> +#if defined(tlb_start_vma) || defined(tlb_end_vma)
> +#error Default tlb_flush() relies on default tlb_start_vma() and
> tlb_end_vma()
> +#endif
> +
> +#define tlb_flush tlb_flush
Do we need this #define?
> @@ -353,19 +387,45 @@ static inline unsigned long tlb_get_unma
> * the vmas are adjusted to only cover the region to be torn down.
> */
> #ifndef tlb_start_vma
> -#define tlb_start_vma(tlb, vma)
> \
> -do { \
> - if (!tlb->fullmm) \
> - flush_cache_range(vma, vma->vm_start, vma->vm_end); \
> -} while (0)
> +#define tlb_start_vma tlb_start_vma
Or this one?
> +static inline void tlb_start_vma(struct mmu_gather *tlb, struct
> vm_area_struct *vma)
> +{
> + if (tlb->fullmm)
> + return;
> +
> + /*
> + * flush_tlb_range() implementations that look at VM_HUGETLB (tile,
> + * mips-4k) flush only large pages.
> + *
> + * flush_tlb_range() implementations that flush I-TLB also flush D-TLB
> + * (tile, xtensa, arm), so it's ok to just add VM_EXEC to an existing
> + * range.
> + *
> + * We rely on tlb_end_vma() to issue a flush, such that when we reset
> + * these values the batch is empty.
> + */
> + tlb->vma_huge = !!(vma->vm_flags & VM_HUGETLB);
> + tlb->vma_exec = !!(vma->vm_flags & VM_EXEC);
Hmm, does this result in code generation for archs that don't care about the
vm_flags?
> + flush_cache_range(vma, vma->vm_start, vma->vm_end);
> +}
> #endif
>
> #ifndef tlb_end_vma
> -#define tlb_end_vma(tlb, vma)
> \
> -do { \
> - if (!tlb->fullmm) \
> - tlb_flush_mmu_tlbonly(tlb); \
> -} while (0)
> +#define tlb_end_vma tlb_end_vma
Another #define we can drop?
Will
