KVM: Add functions to set GFN to private or shared

TDX KVM support needs to track whether GFN is private or shared. Introduce functions to set whether GFN is private or shared and pre-allocate memory for xarray. Suggested-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
intel · Sep 30, 2022 · 60ecd05 · 60ecd05
1 parent 66be339
commit 60ecd05
Show file tree

Hide file tree

Showing 3 changed files with 73 additions and 2 deletions.
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
@@ -49,7 +49,7 @@ config KVM
 	select SRCU
 	select INTERVAL_TREE
 	select HAVE_KVM_PM_NOTIFIER if PM
-	select HAVE_KVM_PRIVATE_MEM if X86_64
+	select HAVE_KVM_PRIVATE_MEM if KVM_MMU_PRIVATE
 	help
 	  Support hosting fully virtualized guest machines using hardware
 	  virtualization extensions.  You will need a fairly recent

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
@@ -2294,9 +2294,20 @@ static inline void kvm_handle_signal_exit(struct kvm_vcpu *vcpu)
 #define KVM_MEM_ATTR_PRIVATE	0x0002
 
 #ifdef __KVM_HAVE_ARCH_UPDATE_MEM_ATTR
+/* memory attr on [start, end) */
+int kvm_vm_reserve_mem_attr(struct kvm *kvm, gfn_t start, gfn_t end);
+int kvm_vm_set_mem_attr(struct kvm *kvm, int attr, gfn_t start, gfn_t end);
 void kvm_arch_update_mem_attr(struct kvm *kvm, unsigned int attr,
 			      gfn_t start, gfn_t end);
 #else
+static inline int kvm_vm_reserve_mem_attr(struct kvm *kvm, gfn_t start, gfn_t end)
+{
+	return -EOPNOTSUPP;
+}
+static inline int kvm_vm_set_mem_attr(struct kvm *kvm, int attr, gfn_t start, gfn_t end)
+{
+	return -EOPNOTSUPP;
+}
 static inline void kvm_arch_update_mem_attr(struct kvm *kvm, unsigned int attr,
 					    gfn_t start, gfn_t end)
 {
@@ -2326,7 +2337,11 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
 {
 	return !xa_load(&kvm->mem_attr_array, gfn);
 }
-
+#else
+static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
+{
+	return false;
+}
 #endif /* CONFIG_HAVE_KVM_PRIVATE_MEM */
 
 #endif
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
@@ -1019,6 +1019,62 @@ static inline void kvm_private_mem_unregister(struct kvm_memory_slot *slot)
 	inaccessible_unregister_notifier(slot->private_file, &slot->notifier);
 }
 
+/*
+ * Reserve memory for [start, end) so that the next set oepration won't fail
+ * with -ENOMEM.
+ */
+int kvm_vm_reserve_mem_attr(struct kvm *kvm, gfn_t start, gfn_t end)
+{
+	int r = 0;
+	gfn_t gfn;
+
+	xa_lock(&kvm->mem_attr_array);
+	for (gfn = start; gfn < end; gfn++) {
+		r = __xa_insert(&kvm->mem_attr_array, gfn, NULL, GFP_KERNEL_ACCOUNT);
+		if (r == -EBUSY)
+			r = 0;
+		if (r)
+			break;
+	}
+	xa_unlock(&kvm->mem_attr_array);
+
+	return r;
+}
+EXPORT_SYMBOL_GPL(kvm_vm_reserve_mem_attr);
+
+/* Set memory attr for [start, end) */
+int kvm_vm_set_mem_attr(struct kvm *kvm, int attr, gfn_t start, gfn_t end)
+{
+	void *entry;
+	gfn_t gfn;
+	int r;
+
+	/* By default, the entry is private. */
+	switch (attr) {
+	case KVM_MEM_ATTR_PRIVATE:
+		entry = NULL;
+		break;
+	case KVM_MEM_ATTR_SHARED:
+		entry = xa_mk_value(KVM_MEM_ATTR_SHARED);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		return -EINVAL;
+	}
+
+	WARN_ON_ONCE(start >= end);
+	for (gfn = start; gfn < end; gfn++) {
+		r = xa_err(xa_store(&kvm->mem_attr_array, gfn, entry,
+				    GFP_KERNEL_ACCOUNT));
+		if (r)
+			break;
+	}
+	if (start < gfn)
+		kvm_arch_update_mem_attr(kvm, attr, start, gfn);
+	return r;
+}
+EXPORT_SYMBOL_GPL(kvm_vm_set_mem_attr);
+
 #else /* !CONFIG_HAVE_KVM_PRIVATE_MEM */
 
 static inline void kvm_private_mem_register(struct kvm_memory_slot *slot)