linux-kernel - Re: [PATCH 1/4] riscv: tlb: fix __p*d_free

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Message-ID: <36166acf-aa32-40b6-806a-ade59bc645ad@ghiti.fr>
Date: Thu, 4 Jan 2024 11:55:40 +0100
From: Alexandre Ghiti <alex@...ti.fr>
To: Jisheng Zhang <jszhang@...nel.org>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 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>,
 Conor Dooley <conor.dooley@...rochip.com>
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-arch@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 1/4] riscv: tlb: fix __p*d_free_tlb()

On 19/12/2023 18:50, Jisheng Zhang wrote:
> If non-leaf PTEs I.E pmd, pud or p4d is modified, a sfence.vma is
> a must for safe, imagine if an implementation caches the non-leaf
> translation in TLB, although I didn't meet this HW so far, but it's
> possible in theory.

And since this is a fix, it would be worth trying to add a Fixes tag 
here. Not easy I agree because it fixes several commits (I have 
07037db5d479f,  e8a62cc26ddf5, d10efa21a9374 and c5e9b2c2ae822 if you 
implement tlb_flush() as I suggested).

So I would add the latest commit as the Fixes commit (which would be 
c5e9b2c2ae822), and then I'd send a patch to stable for each commit with 
the right Fixes tag...@...or: let me know if you have a simpler idea or 
if this is wrong.

Thanks,

Alex

> Signed-off-by: Jisheng Zhang <jszhang@...nel.org>
> ---
>   arch/riscv/include/asm/pgalloc.h | 20 +++++++++++++++++---
>   1 file changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/arch/riscv/include/asm/pgalloc.h b/arch/riscv/include/asm/pgalloc.h
> index d169a4f41a2e..a12fb83fa1f5 100644
> --- a/arch/riscv/include/asm/pgalloc.h
> +++ b/arch/riscv/include/asm/pgalloc.h
> @@ -95,7 +95,13 @@ static inline void pud_free(struct mm_struct *mm, pud_t *pud)
>   		__pud_free(mm, pud);
>   }
>   
> -#define __pud_free_tlb(tlb, pud, addr)  pud_free((tlb)->mm, pud)
> +#define __pud_free_tlb(tlb, pud, addr)					\
> +do {									\
> +	if (pgtable_l4_enabled) {					\
> +		pagetable_pud_dtor(virt_to_ptdesc(pud));		\
> +		tlb_remove_page_ptdesc((tlb), virt_to_ptdesc(pud));	\
> +	}								\
> +} while (0)
>   
>   #define p4d_alloc_one p4d_alloc_one
>   static inline p4d_t *p4d_alloc_one(struct mm_struct *mm, unsigned long addr)
> @@ -124,7 +130,11 @@ static inline void p4d_free(struct mm_struct *mm, p4d_t *p4d)
>   		__p4d_free(mm, p4d);
>   }
>   
> -#define __p4d_free_tlb(tlb, p4d, addr)  p4d_free((tlb)->mm, p4d)
> +#define __p4d_free_tlb(tlb, p4d, addr)					\
> +do {									\
> +	if (pgtable_l5_enabled)						\
> +		tlb_remove_page_ptdesc((tlb), virt_to_ptdesc(p4d));	\
> +} while (0)
>   #endif /* __PAGETABLE_PMD_FOLDED */
>   
>   static inline void sync_kernel_mappings(pgd_t *pgd)
> @@ -149,7 +159,11 @@ static inline pgd_t *pgd_alloc(struct mm_struct *mm)
>   
>   #ifndef __PAGETABLE_PMD_FOLDED
>   
> -#define __pmd_free_tlb(tlb, pmd, addr)  pmd_free((tlb)->mm, pmd)
> +#define __pmd_free_tlb(tlb, pmd, addr)				\
> +do {								\
> +	pagetable_pmd_dtor(virt_to_ptdesc(pmd));		\
> +	tlb_remove_page_ptdesc((tlb), virt_to_ptdesc(pmd));	\
> +} while (0)
>   
>   #endif /* __PAGETABLE_PMD_FOLDED */
>