Re: [PATCH v4 05/12] riscv: mm: Combine the SMP and UP TLB flush code

[Alexandre Ghiti <alexghiti@rivosinc.com>]

On Tue, Jan 2, 2024 at 11:01 PM Samuel Holland
<samuel.holland@sifive.com> wrote:
>
> In SMP configurations, all TLB flushing narrower than flush_tlb_all()
> goes through __flush_tlb_range(). Do the same in UP configurations.
>
> This allows UP configurations to take advantage of recent improvements
> to the code in tlbflush.c, such as support for huge pages and flushing
> multiple-page ranges.
>
> Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
> ---
>
> Changes in v4:
>  - Merge the two copies of __flush_tlb_range() and rely on the compiler
>    to optimize out the broadcast path (both clang and gcc do this)
>  - Merge the two copies of flush_tlb_all() and rely on constant folding
>
> Changes in v2:
>  - Move the SMP/UP merge earlier in the series to avoid build issues
>  - Make a copy of __flush_tlb_range() instead of adding ifdefs inside
>  - local_flush_tlb_all() is the only function used on !MMU (smpboot.c)
>
>  arch/riscv/include/asm/tlbflush.h | 29 +++--------------------------
>  arch/riscv/mm/Makefile            |  5 +----
>  2 files changed, 4 insertions(+), 30 deletions(-)
>
> diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h
> index 8f3418c5f172..7712ffe2f6c4 100644
> --- a/arch/riscv/include/asm/tlbflush.h
> +++ b/arch/riscv/include/asm/tlbflush.h
> @@ -27,12 +27,7 @@ static inline void local_flush_tlb_page(unsigned long addr)
>  {
>         ALT_FLUSH_TLB_PAGE(__asm__ __volatile__ ("sfence.vma %0" : : "r" (addr) : "memory"));
>  }
> -#else /* CONFIG_MMU */
> -#define local_flush_tlb_all()                  do { } while (0)
> -#define local_flush_tlb_page(addr)             do { } while (0)
> -#endif /* CONFIG_MMU */
>
> -#if defined(CONFIG_SMP) && defined(CONFIG_MMU)
>  void flush_tlb_all(void);
>  void flush_tlb_mm(struct mm_struct *mm);
>  void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
> @@ -46,26 +41,8 @@ void flush_tlb_kernel_range(unsigned long start, unsigned long end);
>  void flush_pmd_tlb_range(struct vm_area_struct *vma, unsigned long start,
>                         unsigned long end);
>  #endif
> -#else /* CONFIG_SMP && CONFIG_MMU */
> -
> -#define flush_tlb_all() local_flush_tlb_all()
> -#define flush_tlb_page(vma, addr) local_flush_tlb_page(addr)
> -
> -static inline void flush_tlb_range(struct vm_area_struct *vma,
> -               unsigned long start, unsigned long end)
> -{
> -       local_flush_tlb_all();
> -}
> -
> -/* Flush a range of kernel pages */
> -static inline void flush_tlb_kernel_range(unsigned long start,
> -       unsigned long end)
> -{
> -       local_flush_tlb_all();
> -}
> -
> -#define flush_tlb_mm(mm) flush_tlb_all()
> -#define flush_tlb_mm_range(mm, start, end, page_size) flush_tlb_all()
> -#endif /* !CONFIG_SMP || !CONFIG_MMU */
> +#else /* CONFIG_MMU */
> +#define local_flush_tlb_all()                  do { } while (0)
> +#endif /* CONFIG_MMU */
>
>  #endif /* _ASM_RISCV_TLBFLUSH_H */
> diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile
> index 3a4dfc8babcf..96e65c571ce8 100644
> --- a/arch/riscv/mm/Makefile
> +++ b/arch/riscv/mm/Makefile
> @@ -13,15 +13,12 @@ endif
>  KCOV_INSTRUMENT_init.o := n
>
>  obj-y += init.o
> -obj-$(CONFIG_MMU) += extable.o fault.o pageattr.o
> +obj-$(CONFIG_MMU) += extable.o fault.o pageattr.o tlbflush.o
>  obj-y += cacheflush.o
>  obj-y += context.o
>  obj-y += pgtable.o
>  obj-y += pmem.o
>
> -ifeq ($(CONFIG_MMU),y)
> -obj-$(CONFIG_SMP) += tlbflush.o
> -endif
>  obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
>  obj-$(CONFIG_PTDUMP_CORE) += ptdump.o
>  obj-$(CONFIG_KASAN)   += kasan_init.o
> --
> 2.42.0
>

Nice one, you can add:

Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>

Thanks,

Alex