[RFC PATCH 01/42] KVM: Public header for KVM to export TDP

[Yan Zhao]

Introduce public header for data structures and interfaces for KVM to
export TDP page table (EPT/NPT in x86) to external components of KVM.

KVM exposes a TDP FD object which allows external components to get page
table meta data, request mapping, and register invalidation callbacks to
the TDP page table exported by KVM.

Two symbols kvm_tdp_fd_get() and kvm_tdp_fd_put() are exported by KVM to
external components to get/put the TDP FD object.

New header file kvm_tdp_fd.h is added because kvm_host.h is not expected to
be included from outside of KVM in future AFAIK.

Signed-off-by: Yan Zhao <yan.y.zhao@xxxxxxxxx>
---
 include/linux/kvm_tdp_fd.h | 137 +++++++++++++++++++++++++++++++++++++
 1 file changed, 137 insertions(+)
 create mode 100644 include/linux/kvm_tdp_fd.h

diff --git a/include/linux/kvm_tdp_fd.h b/include/linux/kvm_tdp_fd.h
new file mode 100644
index 0000000000000..3661779dd8cf5
--- /dev/null
+++ b/include/linux/kvm_tdp_fd.h
@@ -0,0 +1,137 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __KVM_TDP_FD_H
+#define __KVM_TDP_FD_H
+
+#include <linux/types.h>
+#include <linux/mm.h>
+
+struct kvm_exported_tdp;
+struct kvm_exported_tdp_ops;
+struct kvm_tdp_importer_ops;
+
+/**
+ * struct kvm_tdp_fd - KVM TDP FD object
+ *
+ * Interface of exporting KVM TDP page table to external components of KVM.
+ *
+ * This KVM TDP FD object is created by KVM VM ioctl KVM_CREATE_TDP_FD.
+ * On object creation, KVM will find or create a TDP page table, mark it as
+ * exported and increase reference count of this exported TDP page table.
+ *
+ * On object destroy, the exported TDP page table is unmarked as exported with
+ * its reference count decreased.
+ *
+ * During the life cycle of KVM TDP FD object, ref count of KVM VM is hold.
+ *
+ * Components outside of KVM can get meta data (e.g. page table type, levels,
+ * root HPA,...), request page fault on the exported TDP page table and register
+ * themselves as importers to receive notification through kvm_exported_tdp_ops
+ * @ops.
+ *
+ * @file:  struct file object associated with the KVM TDP FD object.
+ * @ops:   kvm_exported_tdp_ops associated with the exported TDP page table.
+ * @priv:  internal data structures used by KVM to manage TDP page table
+ *         exported by KVM.
+ *
+ */
+struct kvm_tdp_fd {
+	/* Public */
+	struct file *file;
+	const struct kvm_exported_tdp_ops *ops;
+
+	/* private to KVM */
+	struct kvm_exported_tdp *priv;
+};
+
+/**
+ * kvm_tdp_fd_get - Public interface to get KVM TDP FD object.
+ *
+ * @fd:       fd of the KVM TDP FD object.
+ * @return:   KVM TDP FD object if @fd corresponds to a valid KVM TDP FD file.
+ *            -EBADF if @fd does not correspond a struct file.
+ *            -EINVAL if @fd does not correspond to a KVM TDP FD file.
+ *
+ * Callers of this interface will get a KVM TDP FD object with ref count
+ * increased.
+ */
+struct kvm_tdp_fd *kvm_tdp_fd_get(int fd);
+
+/**
+ * kvm_tdp_fd_put - Public interface to put ref count of a KVM TDP FD object.
+ *
+ * @tdp:  KVM TDP FD object.
+ *
+ * Put reference count of the KVM TDP FD object.
+ * After the last reference count of the TDP FD object goes away,
+ * kvm_tdp_fd_release() will be called to decrease KVM VM ref count and destroy
+ * the KVM TDP FD object.
+ */
+void kvm_tdp_fd_put(struct kvm_tdp_fd *tdp);
+
+struct kvm_tdp_fault_type {
+	u32 read:1;
+	u32 write:1;
+	u32 exec:1;
+};
+
+/**
+ * struct kvm_exported_tdp_ops - operations possible on KVM TDP FD object.
+ * @register_importer:  This is called from components outside of KVM to register
+ *                      importer callback ops and the importer data.
+ *                      This callback is a must.
+ *                      Returns: 0 on success, negative error code on failure.
+ *                              -EBUSY if the importer ops is already registered.
+ * @unregister_importer:This is called from components outside of KVM if it does
+ *                      not want to receive importer callbacks any more.
+ *                      This callback is a must.
+ * @fault:              This is called from components outside of KVM to trigger
+ *                      page fault on a GPA and to map physical page into the
+ *                      TDP page tables exported by KVM.
+ *                      This callback is optional.
+ *                      If this callback is absent, components outside KVM will
+ *                      not be able to trigger page fault and map physical pages
+ *                      into the TDP page tables exported by KVM.
+ * @get_metadata:       This is called from components outside of KVM to retrieve
+ *                      meta data of the TDP page tables exported by KVM, e.g.
+ *                      page table type,root HPA, levels, reserved zero bits...
+ *                      Returns: pointer to a vendor meta data on success.
+ *                               Error PTR on error.
+ *                      This callback is a must.
+ */
+struct kvm_exported_tdp_ops {
+	int (*register_importer)(struct kvm_tdp_fd *tdp_fd,
+				 struct kvm_tdp_importer_ops *ops,
+				 void *importer_data);
+
+	void (*unregister_importer)(struct kvm_tdp_fd *tdp_fd,
+				    struct kvm_tdp_importer_ops *ops);
+
+	int (*fault)(struct kvm_tdp_fd *tdp_fd, struct mm_struct *mm,
+		     unsigned long gfn, struct kvm_tdp_fault_type type);
+
+	void *(*get_metadata)(struct kvm_tdp_fd *tdp_fd);
+};
+
+/**
+ * struct kvm_tdp_importer_ops - importer callbacks
+ *
+ * Components outside of KVM can be registered as importers of KVM's exported
+ * TDP page tables via register_importer op in kvm_exported_tdp_ops of a KVM TDP
+ * FD object.
+ *
+ * Each importer must define its own importer callbacks and KVM will notify
+ * importers of changes of the exported TDP page tables.
+ */
+struct kvm_tdp_importer_ops {
+	/**
+	 * This is called by KVM to notify the importer that a range of KVM
+	 * TDP has been invalidated.
+	 * When @start is 0 and @size is -1, a whole of KVM TDP is invalidated.
+	 *
+	 * @data:    the importer private data.
+	 * @start:   start GPA of the invalidated range.
+	 * @size:    length of in the invalidated range.
+	 */
+	void (*invalidate)(void *data, unsigned long start, unsigned long size);
+};
+#endif /* __KVM_TDP_FD_H */
-- 
2.17.1