Hi Alex,
On 2023-09-11 8:12 AM, Alexandre Ghiti wrote:
> flush_tlb_range() uses a fixed stride of PAGE_SIZE and in its current form,
> when a hugetlb mapping needs to be flushed, flush_tlb_range() flushes the
> whole tlb: so set a stride of the size of the hugetlb mapping in order to
> only flush the hugetlb mapping. However, if the hugepage is a NAPOT region,
> all PTEs that constitute this mapping must be invalidated, so the stride
> size must actually be the size of the PTE.
>
> Note that THPs are directly handled by flush_pmd_tlb_range().
>
> Signed-off-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
> Reviewed-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>
> ---
> arch/riscv/mm/tlbflush.c | 39 ++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 38 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
> index fa03289853d8..5bda6d4fed90 100644
> --- a/arch/riscv/mm/tlbflush.c
> +++ b/arch/riscv/mm/tlbflush.c
> @@ -3,6 +3,7 @@
> #include <linux/mm.h>
> #include <linux/smp.h>
> #include <linux/sched.h>
> +#include <linux/hugetlb.h>
> #include <asm/sbi.h>
> #include <asm/mmu_context.h>
>
> @@ -147,7 +148,43 @@ void flush_tlb_page(struct vm_area_struct *vma, unsigned long addr)
> void flush_tlb_range(struct vm_area_struct *vma, unsigned long start,
> unsigned long end)
> {
> - __flush_tlb_range(vma->vm_mm, start, end - start, PAGE_SIZE);
> + unsigned long stride_size;
> +
> + stride_size = is_vm_hugetlb_page(vma) ?
> + huge_page_size(hstate_vma(vma)) :
> + PAGE_SIZE;
> +
> +#ifdef CONFIG_RISCV_ISA_SVNAPOT
> + /*
> + * As stated in the privileged specification, every PTE in a NAPOT
> + * region must be invalidated, so reset the stride in that case.
> + */
> + if (has_svnapot()) {
This whole block should probably go inside the is_vm_hugetlb_page(vma) check,
since we have to perform that check anyway.
> + unsigned long order, napot_size;
> +
> + for_each_napot_order(order) {
> + napot_size = napot_cont_size(order);
> +
> + if (stride_size != napot_size)
> + continue;
> +
> + if (napot_size >= PGDIR_SIZE)
Can you check stride_size here directly, and drop the loop? We should be able to
assume that the huge page size is valid. Non-NAPOT hugepages will hit one of the
equal-to cases below, which is fine.
Regards,
Samuel
> + stride_size = PGDIR_SIZE;
> + else if (napot_size >= P4D_SIZE)
> + stride_size = P4D_SIZE;
> + else if (napot_size >= PUD_SIZE)
> + stride_size = PUD_SIZE;
> + else if (napot_size >= PMD_SIZE)
> + stride_size = PMD_SIZE;
> + else
> + stride_size = PAGE_SIZE;
> +
> + break;
> + }
> + }
> +#endif
> +
> + __flush_tlb_range(vma->vm_mm, start, end - start, stride_size);
> }
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> void flush_pmd_tlb_range(struct vm_area_struct *vma, unsigned long start,
