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

Chao Peng
2021-11-19T13:50:25Z

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