[PATCH resend v6 26/30] virtio_balloon: disable reporting zeroed optimization for confidential guests

[Michael S. Tsirkin]

In confidential computing environments (TDX, SEV-SNP), the host
is untrusted and may lie about zeroing reported pages. Clear
DEVICE_INIT_REPORTED in validate() so the guest does not skip
re-zeroing based on hints from an untrusted device.

Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Assisted-by: Claude:claude-opus-4-6
Assisted-by: cursor-agent:GPT-5.4-xhigh
---
 drivers/virtio/virtio_balloon.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index e5d11782ce41..d1cdb904d60b 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -18,6 +18,7 @@
 #include <linux/wait.h>
 #include <linux/mm.h>
 #include <linux/page_reporting.h>
+#include <linux/cc_platform.h>
 
 /*
  * Balloon device works in 4K page units.  So each page is pointed to by
@@ -1190,6 +1191,8 @@ static int virtballoon_validate(struct virtio_device *vdev)
 	    !want_init_on_free())
 		__virtio_clear_bit(vdev, VIRTIO_BALLOON_F_DEVICE_INIT_REPORTED);
 
+	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
+		__virtio_clear_bit(vdev, VIRTIO_BALLOON_F_DEVICE_INIT_REPORTED);
 	__virtio_clear_bit(vdev, VIRTIO_F_ACCESS_PLATFORM);
 	return 0;
 }
-- 
MST