[PATCH v6 07/11] KVM: Pass fast_only to kvm_{test_,}age_gfn

[James Houghton <jthoughton@google.com>]

Provide the basics for architectures to implement a fast-only version of
kvm_{test_,}age_gfn.

Add CONFIG_HAVE_KVM_MMU_NOTIFIER_YOUNG_FAST_ONLY that architectures will
set if they non-trivially implement test_young() and clear_young() when
called with fast_only.

Signed-off-by: James Houghton <jthoughton@google.com>
---
 include/linux/kvm_host.h |  1 +
 virt/kvm/Kconfig         |  4 ++++
 virt/kvm/kvm_main.c      | 37 +++++++++++++++++++++----------------
 3 files changed, 26 insertions(+), 16 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 8cd80f969cff..944c5fba2344 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -258,6 +258,7 @@ int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu);
 #ifdef CONFIG_KVM_GENERIC_MMU_NOTIFIER
 union kvm_mmu_notifier_arg {
 	unsigned long attributes;
+	bool fast_only;
 };
 
 struct kvm_gfn_range {
diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index 632334861001..cb4d5384c2f2 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -103,6 +103,10 @@ config KVM_GENERIC_MMU_NOTIFIER
 config KVM_MMU_NOTIFIER_YOUNG_LOCKLESS
        bool
 
+config HAVE_KVM_MMU_NOTIFIER_YOUNG_FAST_ONLY
+       select KVM_GENERIC_MMU_NOTIFIER
+       bool
+
 config KVM_GENERIC_MEMORY_ATTRIBUTES
        depends on KVM_GENERIC_MMU_NOTIFIER
        bool
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 959b6d5d8ce4..86fb2b560d98 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -697,18 +697,20 @@ static __always_inline int kvm_handle_hva_range(struct mmu_notifier *mn,
 static __always_inline int kvm_handle_hva_range_no_flush(struct mmu_notifier *mn,
 							 unsigned long start,
 							 unsigned long end,
-							 gfn_handler_t handler)
+							 gfn_handler_t handler,
+							 bool fast_only)
 {
 	struct kvm *kvm = mmu_notifier_to_kvm(mn);
 	const struct kvm_mmu_notifier_range range = {
-		.start		= start,
-		.end		= end,
-		.handler	= handler,
-		.on_lock	= (void *)kvm_null_fn,
-		.flush_on_ret	= false,
-		.may_block	= false,
-		.lockless	=
+		.start			= start,
+		.end			= end,
+		.handler		= handler,
+		.on_lock		= (void *)kvm_null_fn,
+		.flush_on_ret		= false,
+		.may_block		= false,
+		.lockless		=
 			IS_ENABLED(CONFIG_KVM_MMU_NOTIFIER_YOUNG_LOCKLESS),
+		.arg.fast_only		= fast_only,
 	};
 
 	return __kvm_handle_hva_range(kvm, &range).ret;
@@ -900,7 +902,8 @@ 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,
+					     fast_only);
 }
 
 static int kvm_mmu_notifier_test_young(struct mmu_notifier *mn,
@@ -911,7 +914,7 @@ static int kvm_mmu_notifier_test_young(struct mmu_notifier *mn,
 	trace_kvm_test_age_hva(address, fast_only);
 
 	return kvm_handle_hva_range_no_flush(mn, address, address + 1,
-					     kvm_test_age_gfn);
+					     kvm_test_age_gfn, fast_only);
 }
 
 static void kvm_mmu_notifier_release(struct mmu_notifier *mn,
@@ -926,17 +929,19 @@ static void kvm_mmu_notifier_release(struct mmu_notifier *mn,
 }
 
 static const struct mmu_notifier_ops kvm_mmu_notifier_ops = {
-	.invalidate_range_start	= kvm_mmu_notifier_invalidate_range_start,
-	.invalidate_range_end	= kvm_mmu_notifier_invalidate_range_end,
-	.clear_flush_young	= kvm_mmu_notifier_clear_flush_young,
-	.clear_young		= kvm_mmu_notifier_clear_young,
-	.test_young		= kvm_mmu_notifier_test_young,
-	.release		= kvm_mmu_notifier_release,
+	.invalidate_range_start		= kvm_mmu_notifier_invalidate_range_start,
+	.invalidate_range_end		= kvm_mmu_notifier_invalidate_range_end,
+	.clear_flush_young		= kvm_mmu_notifier_clear_flush_young,
+	.clear_young			= kvm_mmu_notifier_clear_young,
+	.test_young			= kvm_mmu_notifier_test_young,
+	.release			= kvm_mmu_notifier_release,
 };
 
 static int kvm_init_mmu_notifier(struct kvm *kvm)
 {
 	kvm->mmu_notifier.ops = &kvm_mmu_notifier_ops;
+	kvm->mmu_notifier.has_fast_aging =
+		IS_ENABLED(CONFIG_HAVE_KVM_MMU_NOTIFIER_YOUNG_FAST_ONLY);
 	return mmu_notifier_register(&kvm->mmu_notifier, current->mm);
 }
 
-- 
2.46.0.rc1.232.g9752f9e123-goog