Re: [RFC PATCH 33/37] KVM: Move kvm_arch_flush_remote_tlbs_memslot() to common code

Ben Gardon
2022-12-12T22:03:57Z

On Thu, Dec 8, 2022 at 11:40 AM David Matlack <dmatlack@google.com> wrote:
>
> Move kvm_arch_flush_remote_tlbs_memslot() to common code and drop
> "arch_" from the name. kvm_arch_flush_remote_tlbs_memslot() is just a
> range-based TLB invalidation where the range is defined by the memslot.
> Now that kvm_flush_remote_tlbs_range() can be called from common code we
> can just use that and drop a bunch of duplicate code from the arch
> directories.
>
> Note this adds a lockdep assertion for slot_lock being held when calling
> kvm_flush_remote_tlbs_memslot(), which was previously only asserted on
> x86.

Besides the one lockdep assertion, is there any benefit to having this
wrapper function? Open-coding "kvm_flush_remote_tlbs_range(kvm,
memslot->base_gfn, memslot->npages);" is only a slightly longer line
and, IMO, just as readable. I'm happy to see this cleanup, but it
might be just as easy to drop the function.

>
> Signed-off-by: David Matlack <dmatlack@google.com>
> ---
> arch/arm64/kvm/arm.c | 6 ------
> arch/mips/kvm/mips.c | 10 ++--------
> arch/riscv/kvm/mmu.c | 6 ------
> arch/x86/kvm/mmu/mmu.c | 16 +---------------
> arch/x86/kvm/x86.c | 2 +-
> include/linux/kvm_host.h | 7 +++----
> virt/kvm/kvm_main.c | 17 +++++++++++++++--
> 7 files changed, 22 insertions(+), 42 deletions(-)
>
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 0e0d4c4f79a2..4f1549c1d2d2 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -1430,12 +1430,6 @@ void kvm_arch_sync_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot)
>
> }
>
> -void kvm_arch_flush_remote_tlbs_memslot(struct kvm *kvm,
> - const struct kvm_memory_slot *memslot)
> -{
> - kvm_flush_remote_tlbs(kvm);
> -}
> -
> static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
> struct kvm_arm_device_addr *dev_addr)
> {
> diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
> index a25e0b73ee70..ecd8a051fd6b 100644
> --- a/arch/mips/kvm/mips.c
> +++ b/arch/mips/kvm/mips.c
> @@ -209,7 +209,7 @@ void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
> /* Flush slot from GPA */
> kvm_mips_flush_gpa_pt(kvm, slot->base_gfn,
> slot->base_gfn + slot->npages - 1);
> - kvm_arch_flush_remote_tlbs_memslot(kvm, slot);
> + kvm_flush_remote_tlbs_memslot(kvm, slot);
> spin_unlock(&kvm->mmu_lock);
> }
>
> @@ -245,7 +245,7 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
> needs_flush = kvm_mips_mkclean_gpa_pt(kvm, new->base_gfn,
> new->base_gfn + new->npages - 1);
> if (needs_flush)
> - kvm_arch_flush_remote_tlbs_memslot(kvm, new);
> + kvm_flush_remote_tlbs_memslot(kvm, new);
> spin_unlock(&kvm->mmu_lock);
> }
> }
> @@ -997,12 +997,6 @@ int kvm_arch_flush_remote_tlb(struct kvm *kvm)
> return 1;
> }
>
> -void kvm_arch_flush_remote_tlbs_memslot(struct kvm *kvm,
> - const struct kvm_memory_slot *memslot)
> -{
> - kvm_flush_remote_tlbs(kvm);
> -}
> -
> long kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
> {
> long r;
> diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
> index a8281a65cb3d..98bf3719a396 100644
> --- a/arch/riscv/kvm/mmu.c
> +++ b/arch/riscv/kvm/mmu.c
> @@ -406,12 +406,6 @@ void kvm_arch_sync_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot)
> {
> }
>
> -void kvm_arch_flush_remote_tlbs_memslot(struct kvm *kvm,
> - const struct kvm_memory_slot *memslot)
> -{
> - kvm_flush_remote_tlbs(kvm);
> -}
> -
> void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *free)
> {
> }
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 19963ed83484..f2602ee1771f 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -6524,7 +6524,7 @@ static void kvm_rmap_zap_collapsible_sptes(struct kvm *kvm,
> */
> if (slot_handle_level(kvm, slot, kvm_mmu_zap_collapsible_spte,
> PG_LEVEL_4K, KVM_MAX_HUGEPAGE_LEVEL - 1, true))
> - kvm_arch_flush_remote_tlbs_memslot(kvm, slot);
> + kvm_flush_remote_tlbs_memslot(kvm, slot);
> }
>
> void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm,
> @@ -6543,20 +6543,6 @@ void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm,
> }
> }
>
> -void kvm_arch_flush_remote_tlbs_memslot(struct kvm *kvm,
> - const struct kvm_memory_slot *memslot)
> -{
> - /*
> - * All current use cases for flushing the TLBs for a specific memslot
> - * related to dirty logging, and many do the TLB flush out of mmu_lock.
> - * The interaction between the various operations on memslot must be
> - * serialized by slots_locks to ensure the TLB flush from one operation
> - * is observed by any other operation on the same memslot.
> - */
> - lockdep_assert_held(&kvm->slots_lock);
> - kvm_flush_remote_tlbs_range(kvm, memslot->base_gfn, memslot->npages);
> -}
> -
> void kvm_mmu_slot_leaf_clear_dirty(struct kvm *kvm,
> const struct kvm_memory_slot *memslot)
> {
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 517c8ed33542..95ff95da55d5 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -12574,7 +12574,7 @@ static void kvm_mmu_slot_apply_flags(struct kvm *kvm,
> * See is_writable_pte() for more details (the case involving
> * access-tracked SPTEs is particularly relevant).
> */
> - kvm_arch_flush_remote_tlbs_memslot(kvm, new);
> + kvm_flush_remote_tlbs_memslot(kvm, new);
> }
> }
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index d9a7f559d2c5..46ed0ef4fb79 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1366,6 +1366,8 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu, bool usermode_vcpu_not_eligible);
>
> void kvm_flush_remote_tlbs(struct kvm *kvm);
> void kvm_flush_remote_tlbs_range(struct kvm *kvm, gfn_t start_gfn, u64 pages);
> +void kvm_flush_remote_tlbs_memslot(struct kvm *kvm,
> + const struct kvm_memory_slot *memslot);
>
> #ifdef KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE
> int kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int min);
> @@ -1394,10 +1396,7 @@ void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
> unsigned long mask);
> void kvm_arch_sync_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot);
>
> -#ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
> -void kvm_arch_flush_remote_tlbs_memslot(struct kvm *kvm,
> - const struct kvm_memory_slot *memslot);
> -#else /* !CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT */
> +#ifndef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
> int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log);
> int kvm_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log,
> int *is_dirty, struct kvm_memory_slot **memslot);
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 662ca280c0cf..39c2efd15504 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -388,6 +388,19 @@ void __weak kvm_flush_remote_tlbs_range(struct kvm *kvm, gfn_t start_gfn, u64 pa
> kvm_flush_remote_tlbs(kvm);
> }
>
> +void kvm_flush_remote_tlbs_memslot(struct kvm *kvm, const struct kvm_memory_slot *memslot)
> +{
> + /*
> + * All current use cases for flushing the TLBs for a specific memslot
> + * related to dirty logging, and many do the TLB flush out of mmu_lock.
> + * The interaction between the various operations on memslot must be
> + * serialized by slots_locks to ensure the TLB flush from one operation
> + * is observed by any other operation on the same memslot.
> + */
> + lockdep_assert_held(&kvm->slots_lock);
> + kvm_flush_remote_tlbs_range(kvm, memslot->base_gfn, memslot->npages);
> +}
> +
> static void kvm_flush_shadow_all(struct kvm *kvm)
> {
> kvm_arch_flush_shadow_all(kvm);
> @@ -2197,7 +2210,7 @@ static int kvm_get_dirty_log_protect(struct kvm *kvm, struct kvm_dirty_log *log)
> }
>
> if (flush)
> - kvm_arch_flush_remote_tlbs_memslot(kvm, memslot);
> + kvm_flush_remote_tlbs_memslot(kvm, memslot);
>
> if (copy_to_user(log->dirty_bitmap, dirty_bitmap_buffer, n))
> return -EFAULT;
> @@ -2314,7 +2327,7 @@ static int kvm_clear_dirty_log_protect(struct kvm *kvm,
> KVM_MMU_UNLOCK(kvm);
>
> if (flush)
> - kvm_arch_flush_remote_tlbs_memslot(kvm, memslot);
> + kvm_flush_remote_tlbs_memslot(kvm, memslot);
>
> return 0;
> }
> --
> 2.39.0.rc1.256.g54fd8350bd-goog
>