On 7/23/25 7:47 AM, Jason Wang wrote: > On Tue, Jul 22, 2025 at 3:37 PM Paolo Abeni <pab...@redhat.com> wrote: >> >> On 7/22/25 5:28 AM, Jason Wang wrote: >>> On Fri, Jul 18, 2025 at 4:53 PM Paolo Abeni <pab...@redhat.com> wrote: >>>> >>>> Extend the features configuration space to 128 bits, and allow the >>>> common read/write operation to access all of it. >>>> >>>> On migration, save the 128 bit version of the features only if the >>>> upper bits are non zero. Relay reset to clear all the feature >>>> space before load. >>>> >>>> Signed-off-by: Paolo Abeni <pab...@redhat.com> >>> >>> This is a guest noticeable behaviour change. I wonder if we need a >>> command line option to enable and disable this feature for migration >>> compatibility. >> >> This point is not clear to me, could you please elaborate a bit more? do >> you mean we need i.e. a DEFINE_PROP_BOOL() or the like to enable the 128 >> bit space usage? > > Yes, or maybe have a way to let the device to enable it automatically > E.g when UDP GSO is enabled for virtio-net.
I think we can safely enable the extended space access (read/write) if virtio_features_use_ex(vdev->host_features_ex). That should cover also any eventual future addition of more extended features - even of different devices. /P
