On Fri, Nov 1, 2024 at 9:54 AM [off-list ref] wrote:

From: Qiang Zhang <redacted>

Virtio core unconditionally reset and restore status for all virtio
devices before calling restore method. This breaks some virtio drivers
which don't need to do anything in suspend and resume because they
just want to keep device state retained.

The challenge is how can driver know device doesn't need rest.

For example, PCI has no_soft_reset which has been done in the commit
"virtio: Add support for no-reset virtio PCI PM".

And there's a ongoing long discussion of adding suspend support in the
virtio spec, then driver know it's safe to suspend/resume without
reset.

Virtio GPIO is a typical example. GPIO states should be kept unchanged
after suspend and resume (e.g. output pins keep driving the output) and
Virtio GPIO driver does nothing in freeze and restore methods. But the
reset operation in virtio_device_restore breaks this.

Is this mandated by GPIO or virtio spec? If yes, let's quote the revelant part.

Since some devices need reset in suspend and resume while some needn't,
create a new helper function for the original reset and status restore
logic so that virtio drivers can invoke it in their restore method
if necessary.

How are those drivers classified?

Signed-off-by: Qiang Zhang <redacted>

Thanks