Re: [PATCH v1 0/3] virtio-mem: Support VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE

[Michael S. Tsirkin]

On Tue, Nov 30, 2021 at 10:28:35AM +0100, David Hildenbrand wrote:
> 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.
> "
> 
> TODO: Once 6.2 was release, adjust patch #3. Replace patch #1 by a proper
>       Linux header sync.


oh so it's not for 6.2. got it.

> 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>
> 
> 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 6.2 machine on
>     x86
> 
>  hw/i386/pc.c                                |  1 +
>  hw/virtio/virtio-mem.c                      | 63 +++++++++++++++++++++
>  include/hw/virtio/virtio-mem.h              |  8 +++
>  include/standard-headers/linux/virtio_mem.h |  9 ++-
>  4 files changed, 78 insertions(+), 3 deletions(-)
> 
> -- 
> 2.31.1