Re: [PATCH v4 3/7] KVM: Add lockless memslot walk to KVM

Sean Christopherson
2024-05-29T21:51:38Z

On Wed, May 29, 2024, James Houghton wrote:
> @@ -686,10 +694,12 @@ static __always_inline int kvm_handle_hva_range(struct mmu_notifier *mn,
> return __kvm_handle_hva_range(kvm, &range).ret;
> }
>
> -static __always_inline int kvm_handle_hva_range_no_flush(struct mmu_notifier *mn,
> - unsigned long start,
> - unsigned long end,
> - gfn_handler_t handler)
> +static __always_inline int kvm_handle_hva_range_no_flush(
> + struct mmu_notifier *mn,
> + unsigned long start,
> + unsigned long end,
> + gfn_handler_t handler,
> + bool lockless)

Unnecessary and unwanted style change.

> {
> struct kvm *kvm = mmu_notifier_to_kvm(mn);
> const struct kvm_mmu_notifier_range range = {
> @@ -699,6 +709,7 @@ static __always_inline int kvm_handle_hva_range_no_flush(struct mmu_notifier *mn
> .on_lock = (void *)kvm_null_fn,
> .flush_on_ret = false,
> .may_block = false,
> + .lockless = lockless,

Why add @lockess to kvm_handle_hva_range_no_flush()? Both callers immediately
pass %false, and conceptually, locking is always optional for a "no flush" variant.

> };
>
> return __kvm_handle_hva_range(kvm, &range).ret;
> @@ -889,7 +900,8 @@ static int kvm_mmu_notifier_clear_young(struct mmu_notifier *mn,
> * cadence. If we find this inaccurate, we might come up with a
> * more sophisticated heuristic later.
> */
> - return kvm_handle_hva_range_no_flush(mn, start, end, kvm_age_gfn);
> + return kvm_handle_hva_range_no_flush(mn, start, end,
> + kvm_age_gfn, false);
> }
>
> static int kvm_mmu_notifier_test_young(struct mmu_notifier *mn,
> @@ -899,7 +911,7 @@ static int kvm_mmu_notifier_test_young(struct mmu_notifier *mn,
> trace_kvm_test_age_hva(address);
>
> return kvm_handle_hva_range_no_flush(mn, address, address + 1,
> - kvm_test_age_gfn);
> + kvm_test_age_gfn, false);
> }
>
> static void kvm_mmu_notifier_release(struct mmu_notifier *mn,
> --
> 2.45.1.288.g0e0cd299f1-goog