[v4 PATCH] riscv: mm: execute local TLB flush after populating vmemmap

[Vincent Chen]

Sorry, I just discovered a compiler error when CONFIG_SMP is disabled.
Please ignore this patch; I will send the v5 patch to resolve this
issue.


On Wed, Dec 20, 2023 at 9:29 AM Vincent Chen <vincent.chen at sifive.com> 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.
>
> Fixes: d95f1a542c3d ("RISC-V: Implement sparsemem")
> Signed-off-by: Vincent Chen <vincent.chen at sifive.com>
> ---
>  arch/riscv/include/asm/tlbflush.h | 1 +
>  arch/riscv/mm/init.c              | 5 +++++
>  arch/riscv/mm/tlbflush.c          | 6 ++++++
>  3 files changed, 12 insertions(+)
>
> diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h
> index 8f3418c5f172..bf8c52719a3a 100644
> --- a/arch/riscv/include/asm/tlbflush.h
> +++ b/arch/riscv/include/asm/tlbflush.h
> @@ -68,4 +68,5 @@ static inline void flush_tlb_kernel_range(unsigned long start,
>  #define flush_tlb_mm_range(mm, start, end, page_size) flush_tlb_all()
>  #endif /* !CONFIG_SMP || !CONFIG_MMU */
>
> +void local_flush_tlb_kernel_range(unsigned long start, unsigned long end);
>  #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)
> --
> 2.34.1
>