On Mon, Nov 22, 2021 at 05:16:47PM +0300, Kirill A. Shutemov wrote:

On Fri, Nov 19, 2021 at 09:47:39PM +0800, Chao Peng wrote:

quoted

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 <redacted>
Signed-off-by: Chao Peng <redacted>
---
 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;
+	}

I don't think this is enough. The struct kvm can be freed and re-allocated
from the slab and this function will give false-negetive.

Right.

Maybe the kvm has to be tagged with a sequential id that incremented every
allocation. This id can be checked here.

Sounds like a sequential id will be needed, no existing fields in struct
kvm can work for this.

quoted

+
+	return true;
+}

-- 
 Kirill A. Shutemov