linux-kernel - [PATCH v3 17/17] KVM: x86/tdp_mmu: Take root types for kvm_tdp_mmu_invalidate_all

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Date: Wed, 19 Jun 2024 15:36:14 -0700
From: Rick Edgecombe <rick.p.edgecombe@...el.com>
To: seanjc@...gle.com,
	pbonzini@...hat.com,
	kvm@...r.kernel.org
Cc: kai.huang@...el.com,
	dmatlack@...gle.com,
	erdemaktas@...gle.com,
	isaku.yamahata@...il.com,
	linux-kernel@...r.kernel.org,
	sagis@...gle.com,
	yan.y.zhao@...el.com,
	rick.p.edgecombe@...el.com,
	Isaku Yamahata <isaku.yamahata@...el.com>,
	Chao Gao <chao.gao@...el.com>
Subject: [PATCH v3 17/17] KVM: x86/tdp_mmu: Take root types for kvm_tdp_mmu_invalidate_all_roots()

From: Isaku Yamahata <isaku.yamahata@...el.com>

Rename kvm_tdp_mmu_invalidate_all_roots() to
kvm_tdp_mmu_invalidate_roots(), and make it enum kvm_tdp_mmu_root_types
as an argument.

kvm_tdp_mmu_invalidate_roots() is called with different root types. For
kvm_mmu_zap_all_fast() it only operates on shared roots. But when tearing
down a VM it needs to invalidate all roots. Have the callers only
invalidate the required roots instead of all roots.

Within kvm_tdp_mmu_invalidate_roots(), respect the root type
passed by checking the root type in root iterator.

Suggested-by: Chao Gao <chao.gao@...el.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
---
TDX MMU Prep v3:
 - Use root enum instead of process enum (Paolo)
 - Squash with "KVM: x86/tdp_mmu: Invalidate correct roots" (Paolo)
 - Update comment in kvm_mmu_zap_all_fast() (Paolo)
 - Add warning for attempting to invalidate invalid roots (Paolo)

TDX MMU Prep v2:
 - Use process enum instead of root

TDX MMU Prep:
 - New patch
---
 arch/x86/kvm/mmu/mmu.c     |  9 +++++++--
 arch/x86/kvm/mmu/tdp_mmu.c | 15 +++++++++++++--
 arch/x86/kvm/mmu/tdp_mmu.h |  3 ++-
 3 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 287dcc2685e4..c5255aa62146 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -6414,8 +6414,13 @@ static void kvm_mmu_zap_all_fast(struct kvm *kvm)
 	 * write and in the same critical section as making the reload request,
 	 * e.g. before kvm_zap_obsolete_pages() could drop mmu_lock and yield.
 	 */
-	if (tdp_mmu_enabled)
-		kvm_tdp_mmu_invalidate_all_roots(kvm);
+	if (tdp_mmu_enabled) {
+		/*
+		 * External page tables don't support fast zapping, therefore
+		 * their mirrors must be invalidated separately by the caller.
+		 */
+		kvm_tdp_mmu_invalidate_roots(kvm, KVM_DIRECT_ROOTS);
+	}
 
 	/*
 	 * Notify all vcpus to reload its shadow page table and flush TLB.
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 630e6b6d4bf2..a1ab67a4f41f 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -37,7 +37,7 @@ void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm)
 	 * for zapping and thus puts the TDP MMU's reference to each root, i.e.
 	 * ultimately frees all roots.
 	 */
-	kvm_tdp_mmu_invalidate_all_roots(kvm);
+	kvm_tdp_mmu_invalidate_roots(kvm, KVM_VALID_ROOTS);
 	kvm_tdp_mmu_zap_invalidated_roots(kvm);
 
 	WARN_ON(atomic64_read(&kvm->arch.tdp_mmu_pages));
@@ -1110,10 +1110,18 @@ void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm)
  * Note, kvm_tdp_mmu_zap_invalidated_roots() is gifted the TDP MMU's reference.
  * See kvm_tdp_mmu_alloc_root().
  */
-void kvm_tdp_mmu_invalidate_all_roots(struct kvm *kvm)
+void kvm_tdp_mmu_invalidate_roots(struct kvm *kvm,
+				  enum kvm_tdp_mmu_root_types root_types)
 {
 	struct kvm_mmu_page *root;
 
+	/*
+	 * Invalidating invalid roots doesn't make sense, prevent developers from
+	 * having to think about it.
+	 */
+	if (WARN_ON_ONCE(root_types & KVM_INVALID_ROOTS))
+		root_types &= ~KVM_INVALID_ROOTS;
+
 	/*
 	 * mmu_lock must be held for write to ensure that a root doesn't become
 	 * invalid while there are active readers (invalidating a root while
@@ -1135,6 +1143,9 @@ void kvm_tdp_mmu_invalidate_all_roots(struct kvm *kvm)
 	 * or get/put references to roots.
 	 */
 	list_for_each_entry(root, &kvm->arch.tdp_mmu_roots, link) {
+		if (!tdp_mmu_root_match(root, root_types))
+			continue;
+
 		/*
 		 * Note, invalid roots can outlive a memslot update!  Invalid
 		 * roots must be *zapped* before the memslot update completes,
diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h
index 2903f03a34be..56741d31048a 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.h
+++ b/arch/x86/kvm/mmu/tdp_mmu.h
@@ -66,7 +66,8 @@ static inline struct kvm_mmu_page *tdp_mmu_get_root(struct kvm_vcpu *vcpu,
 bool kvm_tdp_mmu_zap_leafs(struct kvm *kvm, gfn_t start, gfn_t end, bool flush);
 bool kvm_tdp_mmu_zap_sp(struct kvm *kvm, struct kvm_mmu_page *sp);
 void kvm_tdp_mmu_zap_all(struct kvm *kvm);
-void kvm_tdp_mmu_invalidate_all_roots(struct kvm *kvm);
+void kvm_tdp_mmu_invalidate_roots(struct kvm *kvm,
+				  enum kvm_tdp_mmu_root_types root_types);
 void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm);
 
 int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault);
-- 
2.34.1