Re: [External] [PATCH v6 06/13] riscv: mm: Combine the SMP and UP TLB flush code

From: yunhui cui <cuiyunhui@bytedance.com>
To: Samuel Holland <samuel.holland@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>,
	linux-riscv@lists.infradead.org,  linux-kernel@vger.kernel.org,
	linux-mm@kvack.org,  Alexandre Ghiti <alexghiti@rivosinc.com>,
	Jisheng Zhang <jszhang@kernel.org>
Subject: Re: [External] [PATCH v6 06/13] riscv: mm: Combine the SMP and UP TLB flush code
Date: Wed, 27 Mar 2024 14:23:56 +0800	[thread overview]
Message-ID: <CAEEQ3wk=0+_vofamg=UWoxFXbH5wZ722vcm5+QuwSdUT6998yw@mail.gmail.com> (raw)
In-Reply-To: <20240327045035.368512-7-samuel.holland@sifive.com>

Hi Samuel,

On Wed, Mar 27, 2024 at 12:51 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.
>
> Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
> Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
> ---
>
> (no changes since v4)
>
> 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/Kconfig                |  2 +-
>  arch/riscv/include/asm/tlbflush.h | 31 +++----------------------------
>  arch/riscv/mm/Makefile            |  5 +----
>  3 files changed, 5 insertions(+), 33 deletions(-)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index be09c8836d56..442532819a44 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -60,7 +60,7 @@ config RISCV
>         select ARCH_USE_MEMTEST
>         select ARCH_USE_QUEUED_RWLOCKS
>         select ARCH_USES_CFI_TRAPS if CFI_CLANG
> -       select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH if SMP && MMU
> +       select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH if MMU
>         select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
>         select ARCH_WANT_FRAME_POINTERS
>         select ARCH_WANT_GENERAL_HUGETLB if !RISCV_ISA_SVNAPOT
> diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h
> index 4112cc8d1d69..4f86424b1ba5 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,
> @@ -54,28 +49,8 @@ void arch_tlbbatch_add_pending(struct arch_tlbflush_unmap_batch *batch,
>                                unsigned long uaddr);
>  void arch_flush_tlb_batched_pending(struct mm_struct *mm);
>  void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch);
> -
> -#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()
> -#define local_flush_tlb_kernel_range(start, end) 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 2c869f8026a8..cbe4d775ef56 100644
> --- a/arch/riscv/mm/Makefile
> +++ b/arch/riscv/mm/Makefile
> @@ -13,14 +13,11 @@ endif
>  KCOV_INSTRUMENT_init.o := n
>
>  obj-y += init.o
> -obj-$(CONFIG_MMU) += extable.o fault.o pageattr.o pgtable.o
> +obj-$(CONFIG_MMU) += extable.o fault.o pageattr.o pgtable.o tlbflush.o
>  obj-y += cacheflush.o
>  obj-y += context.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
> --
> 2.43.1
>

This is cleaner than my previous modification to support UP __flush_tlb_range.
So:
Reviewed-by: Yunhui Cui <cuiyunhui@bytedance.com>

Thanks,
Yunhui