[PATCH v2 0/3] virtio-mem: Support VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE

[David Hildenbrand <david@redhat.com>]

Based-on: 20211208170241.110551-1-cohuck@redhat.com

Support VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE in QEMU, which indicates to
a guest that we don't support reading unplugged memory. We indicate
the feature based on a new "unplugged-inaccessible" property available
for x86 targets only (the only ones with legacy guests). Guests that don't
support VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE will fail initialization if
indicated/required by the hypervisor.

For example, Linux guests starting with v5.16 will support
VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE.

For future targets that don't have legacy guests (especially arm64), we'll
always indicate VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE.

More details can be found in the description of patch #2.

"
For existing compat machines, the property will default to "off", to
not change the behavior but eventually warn about a problematic setup.
Short-term, we'll set the property default to "auto" for new QEMU machines.
Mid-term, we'll set the property default to "on" for new QEMU machines.
Long-term, we'll deprecate the parameter and disallow legacy guests
completely.
"

v1 -> v2:
- Added RBs
- "virtio-mem: Set "unplugged-inaccessible=auto" for the 7.0 machine on
   x86"
-- 6.2 -> 7.0 machine
-- Update aptch description

Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Gavin Shan <gshan@redhat.com>
Cc: Hui Zhu <teawater@gmail.com>
Cc: Sebastien Boeuf <sebastien.boeuf@intel.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Michal Privoznik <mprivozn@redhat.com>

David Hildenbrand (3):
  linux-headers: sync VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE
  virtio-mem: Support VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE
  virtio-mem: Set "unplugged-inaccessible=auto" for the 7.0 machine on
    x86

 hw/i386/pc.c                                |  4 +-
 hw/virtio/virtio-mem.c                      | 63 +++++++++++++++++++++
 include/hw/virtio/virtio-mem.h              |  8 +++
 include/standard-headers/linux/virtio_mem.h |  9 ++-
 4 files changed, 80 insertions(+), 4 deletions(-)

-- 
2.31.1