[PATCH v5 4/6] KVM: arm64: nv: Track guest stage-2 mapping removal

[Wei-Lin Chang]

kvm_stage2_unmap_range() is the helper to remove mappings from the
stage-2 page tables. It is called during guest TLBI handling, memslot
removal, nested mmu reuse, etc.

Teach it about the guest stage-2 tracking trees and remove mappings from
there when shadow mappings are removed. This keeps the tracking trees
from having stale mappings pile up.

Signed-off-by: Wei-Lin Chang <weilin.chang at arm.com>
---
 arch/arm64/include/asm/kvm_host.h   |  5 ++++-
 arch/arm64/include/asm/kvm_nested.h |  2 ++
 arch/arm64/kvm/mmu.c                | 23 +++++++++++++++++++++--
 arch/arm64/kvm/nested.c             | 28 ++++++++++++++++++++++++++++
 4 files changed, 55 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 0695c4ef93f1..0bb83be1dd4f 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -340,7 +340,10 @@ struct kvm_arch {
 	size_t nested_mmus_size;
 	int nested_mmus_next;
 
-	/* Guest s2 tracking trees access serialization. */
+	/*
+	 * Serializes guest s2 tracking trees access when the mmu_lock
+	 * is only held for read.
+	 */
 	spinlock_t guest_s2_tracking_lock;
 
 	/* Interrupt controller */
diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h
index 560b78b3f5ff..ffa3fa01f3cd 100644
--- a/arch/arm64/include/asm/kvm_nested.h
+++ b/arch/arm64/include/asm/kvm_nested.h
@@ -80,6 +80,8 @@ extern void kvm_s2_mmu_iterate_by_vmid(struct kvm *kvm, u16 vmid,
 extern void kvm_record_guest_s2_mapping(struct kvm_s2_mmu *mmu, gpa_t canonical_ipa,
 					gpa_t nested_ipa, size_t map_size,
 					struct kvm_guest_s2_mapping *mapping);
+extern void kvm_remove_guest_s2_mappings(struct kvm_s2_mmu *mmu,
+					 gpa_t nipa, size_t size);
 extern void kvm_vcpu_load_hw_mmu(struct kvm_vcpu *vcpu);
 extern void kvm_vcpu_put_hw_mmu(struct kvm_vcpu *vcpu);
 
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index cea968921041..ddd1bbede227 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -314,6 +314,19 @@ static void invalidate_icache_guest_page(void *va, size_t size)
  * we then fully enforce cacheability of RAM, no matter what the guest
  * does.
  */
+
+static int kvm_pgtable_stage2_unmap_tracked(struct kvm_pgtable *pgt, u64 addr, u64 size)
+{
+	int ret;
+
+	ret = kvm_pgtable_stage2_unmap(pgt, addr, size);
+	if (ret)
+		return ret;
+
+	kvm_remove_guest_s2_mappings(pgt->mmu, addr, size);
+	return 0;
+}
+
 /**
  * __unmap_stage2_range -- Clear stage2 page table entries to unmap a range
  * @mmu:   The KVM stage-2 MMU pointer
@@ -331,11 +344,17 @@ static void __unmap_stage2_range(struct kvm_s2_mmu *mmu, phys_addr_t start, u64
 {
 	struct kvm *kvm = kvm_s2_mmu_to_kvm(mmu);
 	phys_addr_t end = start + size;
+	int (*fn)(struct kvm_pgtable *, u64, u64);
 
 	lockdep_assert_held_write(&kvm->mmu_lock);
 	WARN_ON(size & ~PAGE_MASK);
-	WARN_ON(stage2_apply_range(mmu, start, end, KVM_PGT_FN(kvm_pgtable_stage2_unmap),
-				   may_block));
+
+	if (kvm_is_nested_s2_mmu(kvm, mmu))
+		fn = kvm_pgtable_stage2_unmap_tracked;
+	else
+		fn = KVM_PGT_FN(kvm_pgtable_stage2_unmap);
+
+	WARN_ON(stage2_apply_range(mmu, start, end, fn, may_block));
 }
 
 void kvm_stage2_unmap_range(struct kvm_s2_mmu *mmu, phys_addr_t start,
diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index 646b628bba17..2a4c86df404c 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -877,6 +877,34 @@ void kvm_record_guest_s2_mapping(struct kvm_s2_mmu *mmu, gpa_t canonical_ipa,
 	interval_tree_insert(&mapping->canonical, &kvm->arch.mmu.guest_s2_mappings);
 }
 
+void kvm_remove_guest_s2_mappings(struct kvm_s2_mmu *mmu, gpa_t nipa,
+				  size_t size)
+{
+	struct kvm *kvm = kvm_s2_mmu_to_kvm(mmu);
+	struct interval_tree_node *node, *next;
+	struct kvm_guest_s2_mapping *mapping;
+	gpa_t nipa_end = nipa + size - 1;
+
+	/*
+	 * Guest s2 tracking interval trees are only accessed while holding the
+	 * mmu_lock, hence we don't have to take guest_s2_tracking_lock if the
+	 * mmu_lock is held for write.
+	 */
+	lockdep_assert_held_write(&kvm_s2_mmu_to_kvm(mmu)->mmu_lock);
+
+	node = interval_tree_iter_first(&mmu->guest_s2_mappings, nipa, nipa_end);
+	while (node) {
+		next = interval_tree_iter_next(node, nipa, nipa_end);
+		mapping = container_of(node, struct kvm_guest_s2_mapping,
+				       nested);
+		interval_tree_remove(&mapping->nested, &mmu->guest_s2_mappings);
+		interval_tree_remove(&mapping->canonical,
+				     &kvm->arch.mmu.guest_s2_mappings);
+		kfree(mapping);
+		node = next;
+	}
+}
+
 void kvm_init_nested_s2_mmu(struct kvm_s2_mmu *mmu)
 {
 	/* CnP being set denotes an invalid entry */
-- 
2.43.0