[RFC v2 PATCH 04/13] KVM: Add fd-based memslot data structure and utils

[Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>]

For fd-based memslot store the file references for shared fd and the
private fd (if any) in the memslot structure. Since there is no 'hva'
concept we cannot call hva_to_pfn() to get a pfn, instead kvm_memfd_ops
is added to get_pfn/put_pfn from the memory backing stores that provide
these fds.

Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>
Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
---
 include/linux/kvm_host.h | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 99e9f9969703..1d4ac0c9b63b 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -424,6 +424,12 @@ static inline int kvm_vcpu_exiting_guest_mode(struct kvm_vcpu *vcpu)
  */
 #define KVM_MEM_MAX_NR_PAGES ((1UL << 31) - 1)
 
+struct kvm_memfd_ops {
+	kvm_pfn_t (*get_pfn)(struct kvm_memory_slot *slot, struct file *file,
+			     gfn_t gfn, bool alloc, int *order);
+	void (*put_pfn)(kvm_pfn_t pfn);
+};
+
 struct kvm_memory_slot {
 	gfn_t base_gfn;
 	unsigned long npages;
@@ -433,6 +439,9 @@ struct kvm_memory_slot {
 	u32 flags;
 	short id;
 	u16 as_id;
+	struct file *file;
+	struct file *priv_file;
+	struct kvm_memfd_ops *memfd_ops;
 };
 
 static inline bool kvm_slot_dirty_track_enabled(struct kvm_memory_slot *slot)
@@ -1310,6 +1319,20 @@ static inline int memslot_id(struct kvm *kvm, gfn_t gfn)
 	return gfn_to_memslot(kvm, gfn)->id;
 }
 
+static inline bool memslot_is_memfd(const struct kvm_memory_slot *slot)
+{
+	if (slot && slot->memfd_ops)
+		return true;
+	return false;
+}
+
+static inline bool memslot_has_private(const struct kvm_memory_slot *slot)
+{
+	if (slot && slot->priv_file)
+		return true;
+	return false;
+}
+
 static inline gfn_t
 hva_to_gfn_memslot(unsigned long hva, struct kvm_memory_slot *slot)
 {
-- 
2.17.1