linux-kernel - Re: [PATCH v2] riscv: mm: Fix incorrect ASID argument when flushing TLB

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Date:   Tue, 14 Mar 2023 10:22:43 +0800
From:   Zong Li <zongbox@...il.com>
To:     Dylan Jhong <dylan@...estech.com>
Cc:     linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
        guoren@...nel.org, sergey.matyukevich@...tacore.com,
        aou@...s.berkeley.edu, palmer@...belt.com,
        paul.walmsley@...ive.com, x5710999x@...il.com,
        tim609@...estech.com, peterlin@...estech.com, ycliang@...estech.com
Subject: Re: [PATCH v2] riscv: mm: Fix incorrect ASID argument when flushing TLB

Dylan Jhong <dylan@...estech.com> 於 2023年3月13日 週一 下午12:29寫道：
>
> Currently, we pass the CONTEXTID instead of the ASID to the TLB flush
> function. We should only take the ASID field to prevent from touching
> the reserved bit field.
>
> Fixes: 3f1e782998cd ("riscv: add ASID-based tlbflushing methods")
> Signed-off-by: Dylan Jhong <dylan@...estech.com>
> ---

Hi Dylan,
Thanks for your patch, if I remember correctly, there was a patch from
Alistair Francis did the similar fix. Perhaps we should track that
patch to see why it doesn't be merged. Thanks.

http://lists.infradead.org/pipermail/linux-riscv/2022-March/013558.html

> Changes from v2:
> - Remove unsued EXPORT_SYMBOL()
> ---
>  arch/riscv/include/asm/tlbflush.h | 2 ++
>  arch/riscv/mm/context.c           | 2 +-
>  arch/riscv/mm/tlbflush.c          | 2 +-
>  3 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h
> index 907b9efd39a8..597d6d8aec28 100644
> --- a/arch/riscv/include/asm/tlbflush.h
> +++ b/arch/riscv/include/asm/tlbflush.h
> @@ -12,6 +12,8 @@
>  #include <asm/errata_list.h>
>
>  #ifdef CONFIG_MMU
> +extern unsigned long asid_mask;
> +
>  static inline void local_flush_tlb_all(void)
>  {
>         __asm__ __volatile__ ("sfence.vma" : : : "memory");
> diff --git a/arch/riscv/mm/context.c b/arch/riscv/mm/context.c
> index 80ce9caba8d2..6d1aeb063e81 100644
> --- a/arch/riscv/mm/context.c
> +++ b/arch/riscv/mm/context.c
> @@ -22,7 +22,7 @@ DEFINE_STATIC_KEY_FALSE(use_asid_allocator);
>
>  static unsigned long asid_bits;
>  static unsigned long num_asids;
> -static unsigned long asid_mask;
> +unsigned long asid_mask;
>
>  static atomic_long_t current_version;
>
> diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
> index ce7dfc81bb3f..ba4c27187c95 100644
> --- a/arch/riscv/mm/tlbflush.c
> +++ b/arch/riscv/mm/tlbflush.c
> @@ -27,7 +27,7 @@ static void __sbi_tlb_flush_range(struct mm_struct *mm, unsigned long start,
>         /* check if the tlbflush needs to be sent to other CPUs */
>         broadcast = cpumask_any_but(cmask, cpuid) < nr_cpu_ids;
>         if (static_branch_unlikely(&use_asid_allocator)) {
> -               unsigned long asid = atomic_long_read(&mm->context.id);
> +               unsigned long asid = atomic_long_read(&mm->context.id) & asid_mask;
>
>                 /*
>                  * TLB will be immediately flushed on harts concurrently
> --
> 2.34.1
>