Re: [External] [PATCH -fixes] riscv: Flush the tlb when a page directory is freed

[yunhui cui]

Hi Alexandre,

On Sun, Jan 28, 2024 at 8:04 PM Alexandre Ghiti <alexghiti@rivosinccom> wrote:
>
> The riscv privileged specification mandates to flush the TLB whenever a
> page directory is modified, so add that to tlb_flush().
>
> Fixes: c5e9b2c2ae82 ("riscv: Improve tlb_flush()")
> Signed-off-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
> ---
>  arch/riscv/include/asm/tlb.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/riscv/include/asm/tlb.h b/arch/riscv/include/asm/tlb.h
> index 1eb5682b2af6..50b63b5c15bd 100644
> --- a/arch/riscv/include/asm/tlb.h
> +++ b/arch/riscv/include/asm/tlb.h
> @@ -16,7 +16,7 @@ static void tlb_flush(struct mmu_gather *tlb);
>  static inline void tlb_flush(struct mmu_gather *tlb)
>  {
>  #ifdef CONFIG_MMU
> -       if (tlb->fullmm || tlb->need_flush_all)
> +       if (tlb->fullmm || tlb->need_flush_all || tlb->freed_tables)
>                 flush_tlb_mm(tlb->mm);

Why is it necessary to flush all TLB entries of the process?

Thanks,
Yunhui