[PATCH 1/2] Revert "riscv: mm: notify remote harts about mmu cache updates"

[Guo Ren]

Thx
Reviewed-by: Guo Ren <guoren at kernel.org>

On Sun, Feb 26, 2023 at 11:02 PM Sergey Matyukevich <geomatsi at gmail.com> wrote:
>
> From: Sergey Matyukevich <sergey.matyukevich at syntacore.com>
>
> This reverts the remaining bits of commit 4bd1d80efb5a ("riscv: mm:
> notify remote harts harts about mmu cache updates").
>
> According to bug reports, suggested approach to fix stale TLB entries
> is not sufficient. It needs to be replaced by a more robust solution.
>
> Fixes: 4bd1d80efb5a ("riscv: mm: notify remote harts about mmu cache updates")
> Reported-by: Zong Li <zong.li at sifive.com>
> Reported-by: Lad Prabhakar <prabhakar.mahadev-lad.rj at bp.renesas.com>
> Signed-off-by: Sergey Matyukevich <sergey.matyukevich at syntacore.com>
> Cc: stable at vger.kernel.org
>
> ---
>  arch/riscv/include/asm/mmu.h      |  2 --
>  arch/riscv/include/asm/tlbflush.h | 18 ------------------
>  arch/riscv/mm/context.c           | 10 ----------
>  arch/riscv/mm/tlbflush.c          | 28 +++++++++++++++++-----------
>  4 files changed, 17 insertions(+), 41 deletions(-)
>
> diff --git a/arch/riscv/include/asm/mmu.h b/arch/riscv/include/asm/mmu.h
> index 5ff1f19fd45c..0099dc116168 100644
> --- a/arch/riscv/include/asm/mmu.h
> +++ b/arch/riscv/include/asm/mmu.h
> @@ -19,8 +19,6 @@ typedef struct {
>  #ifdef CONFIG_SMP
>         /* A local icache flush is needed before user execution can resume. */
>         cpumask_t icache_stale_mask;
> -       /* A local tlb flush is needed before user execution can resume. */
> -       cpumask_t tlb_stale_mask;
>  #endif
>  } mm_context_t;
>
> diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h
> index 907b9efd39a8..801019381dea 100644
> --- a/arch/riscv/include/asm/tlbflush.h
> +++ b/arch/riscv/include/asm/tlbflush.h
> @@ -22,24 +22,6 @@ static inline void local_flush_tlb_page(unsigned long addr)
>  {
>         ALT_FLUSH_TLB_PAGE(__asm__ __volatile__ ("sfence.vma %0" : : "r" (addr) : "memory"));
>  }
> -
> -static inline void local_flush_tlb_all_asid(unsigned long asid)
> -{
> -       __asm__ __volatile__ ("sfence.vma x0, %0"
> -                       :
> -                       : "r" (asid)
> -                       : "memory");
> -}
> -
> -static inline void local_flush_tlb_page_asid(unsigned long addr,
> -               unsigned long asid)
> -{
> -       __asm__ __volatile__ ("sfence.vma %0, %1"
> -                       :
> -                       : "r" (addr), "r" (asid)
> -                       : "memory");
> -}
> -
>  #else /* CONFIG_MMU */
>  #define local_flush_tlb_all()                  do { } while (0)
>  #define local_flush_tlb_page(addr)             do { } while (0)
> diff --git a/arch/riscv/mm/context.c b/arch/riscv/mm/context.c
> index 80ce9caba8d2..7acbfbd14557 100644
> --- a/arch/riscv/mm/context.c
> +++ b/arch/riscv/mm/context.c
> @@ -196,16 +196,6 @@ static void set_mm_asid(struct mm_struct *mm, unsigned int cpu)
>
>         if (need_flush_tlb)
>                 local_flush_tlb_all();
> -#ifdef CONFIG_SMP
> -       else {
> -               cpumask_t *mask = &mm->context.tlb_stale_mask;
> -
> -               if (cpumask_test_cpu(cpu, mask)) {
> -                       cpumask_clear_cpu(cpu, mask);
> -                       local_flush_tlb_all_asid(cntx & asid_mask);
> -               }
> -       }
> -#endif
>  }
>
>  static void set_mm_noasid(struct mm_struct *mm)
> diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
> index ce7dfc81bb3f..37ed760d007c 100644
> --- a/arch/riscv/mm/tlbflush.c
> +++ b/arch/riscv/mm/tlbflush.c
> @@ -5,7 +5,23 @@
>  #include <linux/sched.h>
>  #include <asm/sbi.h>
>  #include <asm/mmu_context.h>
> -#include <asm/tlbflush.h>
> +
> +static inline void local_flush_tlb_all_asid(unsigned long asid)
> +{
> +       __asm__ __volatile__ ("sfence.vma x0, %0"
> +                       :
> +                       : "r" (asid)
> +                       : "memory");
> +}
> +
> +static inline void local_flush_tlb_page_asid(unsigned long addr,
> +               unsigned long asid)
> +{
> +       __asm__ __volatile__ ("sfence.vma %0, %1"
> +                       :
> +                       : "r" (addr), "r" (asid)
> +                       : "memory");
> +}
>
>  void flush_tlb_all(void)
>  {
> @@ -15,7 +31,6 @@ void flush_tlb_all(void)
>  static void __sbi_tlb_flush_range(struct mm_struct *mm, unsigned long start,
>                                   unsigned long size, unsigned long stride)
>  {
> -       struct cpumask *pmask = &mm->context.tlb_stale_mask;
>         struct cpumask *cmask = mm_cpumask(mm);
>         unsigned int cpuid;
>         bool broadcast;
> @@ -29,15 +44,6 @@ static void __sbi_tlb_flush_range(struct mm_struct *mm, unsigned long start,
>         if (static_branch_unlikely(&use_asid_allocator)) {
>                 unsigned long asid = atomic_long_read(&mm->context.id);
>
> -               /*
> -                * TLB will be immediately flushed on harts concurrently
> -                * executing this MM context. TLB flush on other harts
> -                * is deferred until this MM context migrates there.
> -                */
> -               cpumask_setall(pmask);
> -               cpumask_clear_cpu(cpuid, pmask);
> -               cpumask_andnot(pmask, pmask, cmask);
> -
>                 if (broadcast) {
>                         sbi_remote_sfence_vma_asid(cmask, start, size, asid);
>                 } else if (size <= stride) {
> --
> 2.39.2
>


-- 
Best Regards
 Guo Ren