[RFC v2 PATCH 13/13] KVM: Enable memfd based page invalidation/fallocate

[Chao Peng]

Since the memory backing store does not get notified when VM is
destroyed so need check if VM is still live in these callbacks.

Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
---
 virt/kvm/memfd.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/virt/kvm/memfd.c b/virt/kvm/memfd.c
index bd930dcb455f..bcfdc685ce22 100644
--- a/virt/kvm/memfd.c
+++ b/virt/kvm/memfd.c
@@ -12,16 +12,38 @@
 #include <linux/memfd.h>
 const static struct guest_mem_ops *memfd_ops;
 
+static bool vm_is_dead(struct kvm *vm)
+{
+       struct kvm *kvm;
+
+       list_for_each_entry(kvm, &vm_list, vm_list) {
+               if (kvm == vm)
+                       return false;
+       }
+
+       return true;
+}
+
 static void memfd_invalidate_page_range(struct inode *inode, void *owner,
                                        pgoff_t start, pgoff_t end)
 {
        //!!!We can get here after the owner no longer exists
+       if (vm_is_dead(owner))
+               return;
+
+       kvm_memfd_invalidate_range(owner, inode, start >> PAGE_SHIFT,
+                                                end >> PAGE_SHIFT);
 }
 
 static void memfd_fallocate(struct inode *inode, void *owner,
                            pgoff_t start, pgoff_t end)
 {
        //!!!We can get here after the owner no longer exists
+       if (vm_is_dead(owner))
+               return;
+
+       kvm_memfd_fallocate_range(owner, inode, start >> PAGE_SHIFT,
+                                               end >> PAGE_SHIFT);
 }
 
 static const struct guest_ops memfd_notifier = {
-- 
2.17.1