kvm: x86/mmu: Allocate and free TDP MMU roots

The TDP MMU must be able to allocate paging structure root pages and track
the usage of those pages. Implement a similar, but separate system for root
page allocation to that of the x86 shadow paging implementation. When
future patches add synchronization model changes to allow for parallel
page faults, these pages will need to be handled differently from the
x86 shadow paging based MMU's root pages.

Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.

This series can be viewed in Gerrit at:
	https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538

Signed-off-by: Ben Gardon <bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 102 insertions, 0 deletions

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index e567e8aa61a1..76ebb5898dd7 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -1,6 +1,9 @@
 // SPDX-License-Identifier: GPL-2.0
 
+#include "mmu.h"
+#include "mmu_internal.h"
 #include "tdp_mmu.h"
+#include "spte.h"
 
 static bool __read_mostly tdp_mmu_enabled = false;
 
@@ -21,10 +24,109 @@ void kvm_mmu_init_tdp_mmu(struct kvm *kvm)
 
 	/* This should not be changed for the lifetime of the VM. */
 	kvm->arch.tdp_mmu_enabled = true;
+
+	INIT_LIST_HEAD(&kvm->arch.tdp_mmu_roots);
 }
 
 void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm)
 {
 	if (!kvm->arch.tdp_mmu_enabled)
 		return;
+
+	WARN_ON(!list_empty(&kvm->arch.tdp_mmu_roots));
+}
+
+#define for_each_tdp_mmu_root(_kvm, _root)			    \
+	list_for_each_entry(_root, &_kvm->arch.tdp_mmu_roots, link)
+
+bool is_tdp_mmu_root(struct kvm *kvm, hpa_t hpa)
+{
+	struct kvm_mmu_page *sp;
+
+	sp = to_shadow_page(hpa);
+
+	return sp->tdp_mmu_page && sp->root_count;
+}
+
+void kvm_tdp_mmu_free_root(struct kvm *kvm, struct kvm_mmu_page *root)
+{
+	lockdep_assert_held(&kvm->mmu_lock);
+
+	WARN_ON(root->root_count);
+	WARN_ON(!root->tdp_mmu_page);
+
+	list_del(&root->link);
+
+	free_page((unsigned long)root->spt);
+	kmem_cache_free(mmu_page_header_cache, root);
+}
+
+static union kvm_mmu_page_role page_role_for_level(struct kvm_vcpu *vcpu,
+						   int level)
+{
+	union kvm_mmu_page_role role;
+
+	role = vcpu->arch.mmu->mmu_role.base;
+	role.level = level;
+	role.direct = true;
+	role.gpte_is_8_bytes = true;
+	role.access = ACC_ALL;
+
+	return role;
+}
+
+static struct kvm_mmu_page *alloc_tdp_mmu_page(struct kvm_vcpu *vcpu, gfn_t gfn,
+					       int level)
+{
+	struct kvm_mmu_page *sp;
+
+	sp = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_page_header_cache);
+	sp->spt = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_shadow_page_cache);
+	set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
+
+	sp->role.word = page_role_for_level(vcpu, level).word;
+	sp->gfn = gfn;
+	sp->tdp_mmu_page = true;
+
+	return sp;
+}
+
+static struct kvm_mmu_page *get_tdp_mmu_vcpu_root(struct kvm_vcpu *vcpu)
+{
+	union kvm_mmu_page_role role;
+	struct kvm *kvm = vcpu->kvm;
+	struct kvm_mmu_page *root;
+
+	role = page_role_for_level(vcpu, vcpu->arch.mmu->shadow_root_level);
+
+	spin_lock(&kvm->mmu_lock);
+
+	/* Check for an existing root before allocating a new one. */
+	for_each_tdp_mmu_root(kvm, root) {
+		if (root->role.word == role.word) {
+			kvm_mmu_get_root(kvm, root);
+			spin_unlock(&kvm->mmu_lock);
+			return root;
+		}
+	}
+
+	root = alloc_tdp_mmu_page(vcpu, 0, vcpu->arch.mmu->shadow_root_level);
+	root->root_count = 1;
+
+	list_add(&root->link, &kvm->arch.tdp_mmu_roots);
+
+	spin_unlock(&kvm->mmu_lock);
+
+	return root;
+}
+
+hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu)
+{
+	struct kvm_mmu_page *root;
+
+	root = get_tdp_mmu_vcpu_root(vcpu);
+	if (!root)
+		return INVALID_PAGE;
+
+	return __pa(root->spt);
 }