[PATCH v4 05/12] KVM: Extend the memslot to support fd-based private memory

[Chao Peng]

Extend the memslot definition to provide fd-based private memory support
by adding two new fields (private_fd/private_offset). The memslot then
can maintain memory for both shared pages and private pages in a single
memslot. Shared pages are provided by existing userspace_addr(hva) field
and private pages are provided through the new private_fd/private_offset
fields.

Since there is no 'hva' concept anymore for private memory so we cannot
rely on get_user_pages() to get a pfn, instead we use the newly added
memfile_notifier to complete the same job.

This new extension is indicated by a new flag KVM_MEM_PRIVATE.

Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>
Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
---
 include/linux/kvm_host.h | 7 +++++++
 include/uapi/linux/kvm.h | 8 ++++++++
 2 files changed, 15 insertions(+)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index f079820f52b5..5011ac35bc50 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -458,8 +458,15 @@ struct kvm_memory_slot {
 	u32 flags;
 	short id;
 	u16 as_id;
+	struct file *private_file;
+	loff_t private_offset;
 };
 
+static inline bool kvm_slot_is_private(const struct kvm_memory_slot *slot)
+{
+	return slot && (slot->flags & KVM_MEM_PRIVATE);
+}
+
 static inline bool kvm_slot_dirty_track_enabled(const struct kvm_memory_slot *slot)
 {
 	return slot->flags & KVM_MEM_LOG_DIRTY_PAGES;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index fbfd70d965c6..5d6dceb1b93e 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -103,6 +103,13 @@ struct kvm_userspace_memory_region {
 	__u64 userspace_addr; /* start of the userspace allocated memory */
 };
 
+struct kvm_userspace_memory_region_ext {
+	struct kvm_userspace_memory_region region;
+	__u64 private_offset;
+	__u32 private_fd;
+	__u32 padding[5];
+};
+
 /*
  * The bit 0 ~ bit 15 of kvm_memory_region::flags are visible for userspace,
  * other bits are reserved for kvm internal use which are defined in
@@ -110,6 +117,7 @@ struct kvm_userspace_memory_region {
  */
 #define KVM_MEM_LOG_DIRTY_PAGES	(1UL << 0)
 #define KVM_MEM_READONLY	(1UL << 1)
+#define KVM_MEM_PRIVATE		(1UL << 2)
 
 /* for KVM_IRQ_LINE */
 struct kvm_irq_level {
-- 
2.17.1