[PATCH v5] riscv: mm: execute local TLB flush after populating vmemmap

[Vincent Chen]

On Thu, Dec 21, 2023 at 5:19 AM Alexandre Ghiti <alex at ghiti.fr> wrote:
>
> Hi Vincent,
>
> On 20/12/2023 03:43, Vincent Chen wrote:
> > The spare_init() calls memmap_populate() many times to create VA to PA
> > mapping for the VMEMMAP area, where all "struct page" are located once
> > CONFIG_SPARSEMEM_VMEMMAP is defined. These "struct page" are later
> > initialized in the zone_sizes_init() function. However, during this
> > process, no sfence.vma instruction is executed for this VMEMMAP area.
> > This omission may cause the hart to fail to perform page table walk
> > because some data related to the address translation is invisible to the
> > hart. To solve this issue, the local_flush_tlb_kernel_range() is called
> > right after the spare_init() to execute a sfence.vma instruction for this
> > VMEMMAP area, ensuring that all data related to the address translation
> > is visible to the hart.
>
>
> s/spare_init/sparse_init
>
>
> >
> > Fixes: d95f1a542c3d ("RISC-V: Implement sparsemem")
> > Signed-off-by: Vincent Chen <vincent.chen at sifive.com>
> > ---
> >   arch/riscv/include/asm/tlbflush.h | 2 ++
> >   arch/riscv/mm/init.c              | 5 +++++
> >   arch/riscv/mm/tlbflush.c          | 6 ++++++
> >   3 files changed, 13 insertions(+)
> >
> > diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h
> > index 8f3418c5f172..525267379ccb 100644
> > --- a/arch/riscv/include/asm/tlbflush.h
> > +++ b/arch/riscv/include/asm/tlbflush.h
> > @@ -46,6 +46,7 @@ void flush_tlb_kernel_range(unsigned long start, unsigned long end);
> >   void flush_pmd_tlb_range(struct vm_area_struct *vma, unsigned long start,
> >                       unsigned long end);
> >   #endif
> > +void local_flush_tlb_kernel_range(unsigned long start, unsigned long end);
> >   #else /* CONFIG_SMP && CONFIG_MMU */
> >
> >   #define flush_tlb_all() local_flush_tlb_all()
> > @@ -66,6 +67,7 @@ static inline void flush_tlb_kernel_range(unsigned long start,
> >
> >   #define flush_tlb_mm(mm) flush_tlb_all()
> >   #define flush_tlb_mm_range(mm, start, end, page_size) flush_tlb_all()
> > +#define local_flush_tlb_kernel_range(start, end) flush_tlb_all()
> >   #endif /* !CONFIG_SMP || !CONFIG_MMU */
> >
> >   #endif /* _ASM_RISCV_TLBFLUSH_H */
> > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> > index 2e011cbddf3a..cc56a0945120 100644
> > --- a/arch/riscv/mm/init.c
> > +++ b/arch/riscv/mm/init.c
> > @@ -1377,6 +1377,10 @@ void __init misc_mem_init(void)
> >       early_memtest(min_low_pfn << PAGE_SHIFT, max_low_pfn << PAGE_SHIFT);
> >       arch_numa_init();
> >       sparse_init();
> > +#ifdef CONFIG_SPARSEMEM_VMEMMAP
> > +     /* The entire VMEMMAP region has been populated. Flush TLB for this region */
> > +     local_flush_tlb_kernel_range(VMEMMAP_START, VMEMMAP_END);
> > +#endif
> >       zone_sizes_init();
> >       arch_reserve_crashkernel();
> >       memblock_dump_all();
> > @@ -1386,6 +1390,7 @@ void __init misc_mem_init(void)
> >   int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> >                              struct vmem_altmap *altmap)
> >   {
> > +     /* Defer the required TLB flush until the entire VMEMMAP region has been populated */
> >       return vmemmap_populate_basepages(start, end, node, NULL);
> >   }
> >   #endif
> > diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
> > index e6659d7368b3..d11a4ae87ec1 100644
> > --- a/arch/riscv/mm/tlbflush.c
> > +++ b/arch/riscv/mm/tlbflush.c
> > @@ -193,6 +193,12 @@ void flush_tlb_kernel_range(unsigned long start, unsigned long end)
> >       __flush_tlb_range(NULL, start, end - start, PAGE_SIZE);
> >   }
> >
> > +/* Flush a range of kernel pages without broadcasting */
> > +void local_flush_tlb_kernel_range(unsigned long start, unsigned long end)
> > +{
> > +     local_flush_tlb_range_asid(start, end - start, PAGE_SIZE, FLUSH_TLB_NO_ASID);
> > +}
> > +
> >   #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> >   void flush_pmd_tlb_range(struct vm_area_struct *vma, unsigned long start,
> >                       unsigned long end)
>
>
> Otherwise, this looks good to me and should go to -fixes, you can add:
>
> Reviewed-by: Alexandre Ghiti <alexghiti at rivosinc.com>
>
> Thanks!

Apologies for the delayed response, and thank you for the review. I
will fix the typo and add your 'Reviewed-by' in the v6 patch.

Vincent
>
> Alex
>