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

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Message-ID: <CAEEQ3wmXvnqdvv39JZhkfUsoLbJr4B2WwdgWnGY=aHgE8A-+0g@mail.gmail.com>
Date: Mon, 29 Jan 2024 11:06:56 +0800
From: yunhui cui <cuiyunhui@...edance.com>
To: Alexandre Ghiti <alexghiti@...osinc.com>
Cc: Will Deacon <will@...nel.org>, "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Nick Piggin <npiggin@...il.com>, 
	Peter Zijlstra <peterz@...radead.org>, Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	Samuel Holland <samuel.holland@...ive.com>, Andrew Jones <ajones@...tanamicro.com>, 
	linux-arch@...r.kernel.org, linux-mm@...ck.org, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [External] [PATCH -fixes] riscv: Flush the tlb when a page
 directory is freed

Hi Alexandre,

On Sun, Jan 28, 2024 at 8:04 PM Alexandre Ghiti <alexghiti@...osinccom> 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@...osinc.com>
> ---
>  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