Re: [PATCH] riscv: mm: Fix incorrect ASID argument when flushing TLB

[Guo Ren]

On Fri, Mar 10, 2023 at 6:32 PM Dylan Jhong <dylan@xxxxxxxxxxxxx> wrote:
>
> 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@xxxxxxxxxxxxx>
> ---
>  arch/riscv/include/asm/tlbflush.h | 2 ++
>  arch/riscv/mm/context.c           | 3 ++-
>  arch/riscv/mm/tlbflush.c          | 2 +-
>  3 files changed, 5 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..a6b76b33e377 100644
> --- a/arch/riscv/mm/context.c
> +++ b/arch/riscv/mm/context.c
> @@ -22,7 +22,8 @@ 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;
> +EXPORT_SYMBOL(asid_mask);
Why EXPORT_SYMBOL? (No module would use it by your patch.)

>
>  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
>


-- 
Best Regards
 Guo Ren