diff options
authorLinus Torvalds <>2021-11-13 13:14:05 -0800
committerLinus Torvalds <>2021-11-13 13:14:05 -0800
commitccfff0a2bd2a30de130b5623d242ddecd0272bc2 (patch)
parent3ad7befd4842afa2449026715987122a1c6dcb85 (diff)
parent61082ad6a6e1f999eef7e7e90046486c87933b1e (diff)
Merge tag 'virtio-mem-for-5.16' of git://
Pull virtio-mem update from David Hildenbrand: "Support the VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE feature in virtio-mem, now that "accidential" access to logically unplugged memory inside added Linux memory blocks is no longer possible, because we: - Removed /dev/kmem in commit bbcd53c96071 ("drivers/char: remove /dev/kmem for good") - Disallowed access to virtio-mem device memory via /dev/mem in commit 2128f4e21aa ("virtio-mem: disallow mapping virtio-mem memory via /dev/mem") - Sanitized access to virtio-mem device memory via /proc/kcore in commit 0daa322b8ff9 ("fs/proc/kcore: don't read offline sections, logically offline pages and hwpoisoned pages") - Sanitized access to virtio-mem device memory via /proc/vmcore in commit ce2814622e84 ("virtio-mem: kdump mode to sanitize /proc/vmcore access") The new VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE feature that will be required by some hypervisors implementing virtio-mem in the near future, so let's support it now that we safely can" * tag 'virtio-mem-for-5.16' of git:// virtio-mem: support VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE
2 files changed, 7 insertions, 3 deletions
diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index 0da0af251c73..96e5a8782769 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -2889,6 +2889,7 @@ static unsigned int virtio_mem_features[] = {
#if defined(CONFIG_NUMA) && defined(CONFIG_ACPI_NUMA)
static const struct virtio_device_id virtio_mem_id_table[] = {
diff --git a/include/uapi/linux/virtio_mem.h b/include/uapi/linux/virtio_mem.h
index 70e01c687d5e..e9122f1d0e0c 100644
--- a/include/uapi/linux/virtio_mem.h
+++ b/include/uapi/linux/virtio_mem.h
@@ -68,9 +68,10 @@
* explicitly triggered (VIRTIO_MEM_REQ_UNPLUG).
* There are no guarantees what will happen if unplugged memory is
- * read/written. Such memory should, in general, not be touched. E.g.,
- * even writing might succeed, but the values will simply be discarded at
- * random points in time.
+ * read/written. In general, unplugged memory should not be touched, because
+ * the resulting action is undefined. There is one exception: without
+ * VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE, unplugged memory inside the usable
+ * region can be read, to simplify creation of memory dumps.
* It can happen that the device cannot process a request, because it is
* busy. The device driver has to retry later.
@@ -87,6 +88,8 @@
/* node_id is an ACPI PXM and is valid */
+/* unplugged memory must not be accessed */
/* --- virtio-mem: guest -> host requests --- */