On Tue, Jan 2, 2024 at 11:01 PM Samuel Holland
<samuel.holland@xxxxxxxxxx> wrote:
>
> __flush_tlb_range() avoids broadcasting TLB flushes when an mm context
> is only active on the local CPU. Apply this same optimization to TLB
> flushes of kernel memory when only one CPU is online. This check can be
> constant-folded when SMP is disabled.
>
> Signed-off-by: Samuel Holland <samuel.holland@xxxxxxxxxx>
> ---
>
> Changes in v4:
> - New patch for v4
>
> arch/riscv/mm/tlbflush.c | 17 ++++++-----------
> 1 file changed, 6 insertions(+), 11 deletions(-)
>
> diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
> index 09b03bf71e6a..2f18fe6fc4f3 100644
> --- a/arch/riscv/mm/tlbflush.c
> +++ b/arch/riscv/mm/tlbflush.c
> @@ -98,27 +98,23 @@ static void __flush_tlb_range(struct mm_struct *mm, unsigned long start,
> {
> const struct cpumask *cmask;
> unsigned long asid = FLUSH_TLB_NO_ASID;
> - bool broadcast;
> + unsigned int cpu;
>
> if (mm) {
> - unsigned int cpuid;
> -
> cmask = mm_cpumask(mm);
> if (cpumask_empty(cmask))
> return;
>
> - cpuid = get_cpu();
> - /* check if the tlbflush needs to be sent to other CPUs */
> - broadcast = cpumask_any_but(cmask, cpuid) < nr_cpu_ids;
> -
> if (static_branch_unlikely(&use_asid_allocator))
> asid = atomic_long_read(&mm->context.id) & asid_mask;
> } else {
> cmask = cpu_online_mask;
> - broadcast = true;
> }
>
> - if (!broadcast) {
> + cpu = get_cpu();
> +
> + /* Check if the TLB flush needs to be sent to other CPUs. */
> + if (cpumask_any_but(cmask, cpu) >= nr_cpu_ids) {
> local_flush_tlb_range_asid(start, size, stride, asid);
> } else if (riscv_use_sbi_for_rfence()) {
> sbi_remote_sfence_vma_asid(cmask, start, size, asid);
> @@ -132,8 +128,7 @@ static void __flush_tlb_range(struct mm_struct *mm, unsigned long start,
> on_each_cpu_mask(cmask, __ipi_flush_tlb_range_asid, &ftd, 1);
> }
>
> - if (mm)
> - put_cpu();
> + put_cpu();
> }
>
> void flush_tlb_mm(struct mm_struct *mm)
> --
> 2.42.0
>
You can add:
Reviewed-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
Thanks,
Alex
