Messages in this thread | | | Date | Fri, 03 Apr 2020 09:03:31 -0700 (PDT) | Subject | Re: [PATCH] riscv: mm: synchronize MMU after page table update | From | Palmer Dabbelt <> |
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On Mon, 23 Mar 2020 22:49:45 PDT (-0700), nickhu@andestech.com wrote: > Similar to commit bf587caae305 ("riscv: mm: synchronize MMU after pte change") > > For those riscv implementations whose TLB cannot synchronize with dcache, > an SFENCE.VMA is necessary after page table update. > This patch fixed two functions: > > 1. pgd_alloc > During fork, a parent process prepares pgd for its child and updates satp > later, but they may not run on the same core. Adding a remote SFENCE.VMA to > invalidate TLB in other cores is needed. Thus use flush_tlb_all() instead > of local_flush_tlb_all() here. > Similar approaches can be found in arm and csky. > > 2. __set_fixmap > Add a SFENCE.VMA after fixmap pte update. > Similar approaches can be found in arm and sh. > > Signed-off-by: Nick Hu <nickhu@andestech.com> > Signed-off-by: Nylon Chen <nylon7@andestech.com> > Cc: Alan Kao <alankao@andestech.com> > --- > arch/riscv/include/asm/pgalloc.h | 1 + > arch/riscv/mm/init.c | 2 +- > 2 files changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/riscv/include/asm/pgalloc.h b/arch/riscv/include/asm/pgalloc.h > index 3f601ee8233f..071468fa14b7 100644 > --- a/arch/riscv/include/asm/pgalloc.h > +++ b/arch/riscv/include/asm/pgalloc.h > @@ -51,6 +51,7 @@ static inline pgd_t *pgd_alloc(struct mm_struct *mm) > memcpy(pgd + USER_PTRS_PER_PGD, > init_mm.pgd + USER_PTRS_PER_PGD, > (PTRS_PER_PGD - USER_PTRS_PER_PGD) * sizeof(pgd_t)); > + flush_tlb_all(); > } > return pgd; > } > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c > index fab855963c73..a7f329503ed0 100644 > --- a/arch/riscv/mm/init.c > +++ b/arch/riscv/mm/init.c > @@ -203,8 +203,8 @@ void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot) > set_pte(ptep, pfn_pte(phys >> PAGE_SHIFT, prot)); > } else { > pte_clear(&init_mm, addr, ptep); > - local_flush_tlb_page(addr); > } > + local_flush_tlb_page(addr); > } > > static pte_t *__init get_pte_virt(phys_addr_t pa)
As a general rule, any fences are supposed to have a comment describing why they're there. The generic fences will be caught by checkpatch, but I don't remember if these are.
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