Re: [PATCH v4 3/5] RISC-V: KVM: Remove redundant TLB flush operations

On Wed, Jul 1, 2026 at 5:41 PM Wang Yechao <[email protected]> wrote:
>
> The function kvm_arch_mmu_enable_log_dirty_pt_masked() is invoked from
> two distinct call paths:
>
> kvm_clear_dirty_log_protect()
>   kvm_arch_mmu_enable_log_dirty_pt_masked()
>
> kvm_vm_ioctl_reset_dirty_pages()
>   kvm_dirty_ring_reset()
>     kvm_reset_dirty_gfn()
>         kvm_arch_mmu_enable_log_dirty_pt_masked()
>
> In both scenarios, the caller already performs a remote TLB flush after
> dirty logging is enabled, so the TLB flush inside
> kvm_arch_mmu_enable_log_dirty_pt_masked() is unnecessary. Remove it.
>
> Signed-off-by: Wang Yechao <[email protected]>
> ---
>  arch/riscv/kvm/mmu.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
>
> diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
> index 363238efaedb4..056c0abe278af 100644
> --- a/arch/riscv/kvm/mmu.c
> +++ b/arch/riscv/kvm/mmu.c
> @@ -162,14 +162,10 @@ void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
>         phys_addr_t start = (base_gfn +  __ffs(mask)) << PAGE_SHIFT;
>         phys_addr_t end = (base_gfn + __fls(mask) + 1) << PAGE_SHIFT;
>         struct kvm_gstage gstage;
> -       bool flush;
>
>         kvm_riscv_gstage_init(&gstage, kvm);
>
> -       flush = kvm_riscv_gstage_wp_range(&gstage, start, end);
> -       if (flush)
> -               kvm_flush_remote_tlbs_range(kvm, start >> PAGE_SHIFT,
> -                                           (end - start) >> PAGE_SHIFT);
> +       kvm_riscv_gstage_wp_range(&gstage, start, end);

Please add comment here that remote TLB flush is not needed here
since callers of kvm_arch_mmu_enable_log_dirty_pt_masked() already
do it.

>  }
>
>  void kvm_arch_sync_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot)
> --
> 2.43.5
>

Otherwise, this looks good to me.

Reviewed-by: Anup Patel <[email protected]>

Thanks,
Anup

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