Messages in this thread | | | Date | Wed, 7 Feb 2024 08:28:01 +0100 | Subject | Re: [PATCH 1/4] riscv: tlb: fix __p*d_free_tlb() | From | Alexandre Ghiti <> |
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Hi Jisheng,
On 31/12/2023 07:21, Alexandre Ghiti wrote: > 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();
I sent a patch for that here https://lore.kernel.org/linux-riscv/20240128120405.25876-1-alexghiti@rivosinc.com/
You can add:
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Thanks,
Alex
> > 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 */ >
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