From: Alexandre Ghiti <alex@ghiti.fr>
To: Jisheng Zhang <jszhang@kernel.org>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>, Will Deacon <will@kernel.org>,
"Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Nick Piggin <npiggin@gmail.com>,
Peter Zijlstra <peterz@infradead.org>
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
linux-arch@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 1/4] riscv: tlb: fix __p*d_free_tlb()
Date: Sun, 31 Dec 2023 07:21:38 +0100 [thread overview]
Message-ID: <08f55d3e-d68e-406a-9bc9-d62f3c86e949@ghiti.fr> (raw)
In-Reply-To: <20231219175046.2496-2-jszhang@kernel.org>
Hi Jisheng,
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.
>
> Signed-off-by: Jisheng Zhang<jszhang@kernel.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)); \
The specification indeed states that an sfence.vma must be emitted after
a page directory modification. Your change is not enough though since
eventually tlb_flush() is called and in this function we should add:
if (tlb->freed_tables)
tlb_flush_mm();
otherwise we are not guaranteed that a "global" sfence.vma is called.
Would you be able to benchmark this change and see the performance impact?
Thanks,
Alex
> + } \
> +} 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 */
>
next prev parent reply other threads:[~2023-12-31 6:21 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-19 17:50 [PATCH 0/4] riscv: support fast gup Jisheng Zhang
2023-12-19 17:50 ` [PATCH 1/4] riscv: tlb: fix __p*d_free_tlb() Jisheng Zhang
2023-12-31 6:21 ` Alexandre Ghiti [this message]
2024-02-07 7:28 ` Alexandre Ghiti
2024-01-04 10:55 ` Alexandre Ghiti
2024-01-10 14:52 ` Palmer Dabbelt
2023-12-19 17:50 ` [PATCH 2/4] riscv: tlb: convert __p*d_free_tlb() to inline functions Jisheng Zhang
2023-12-20 2:59 ` [External] " yunhui cui
2023-12-20 12:57 ` Jisheng Zhang
2023-12-31 6:24 ` Alexandre Ghiti
2023-12-19 17:50 ` [PATCH 3/4] riscv: enable MMU_GATHER_RCU_TABLE_FREE for SMP && MMU Jisheng Zhang
2023-12-31 6:32 ` Alexandre Ghiti
2024-01-02 3:23 ` Jisheng Zhang
2024-01-04 10:45 ` Alexandre Ghiti
2023-12-19 17:50 ` [PATCH 4/4] riscv: enable HAVE_FAST_GUP if MMU Jisheng Zhang
2023-12-31 6:37 ` Alexandre Ghiti
2024-01-02 3:25 ` Jisheng Zhang
2024-01-04 10:46 ` Alexandre Ghiti
2024-01-25 21:30 ` [PATCH 0/4] riscv: support fast gup patchwork-bot+linux-riscv
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