The refcounts actually correspond to 'active_ref' structures stored in a
GHashTable per "user" on the backend side (mostly, per XenDevice).
If we zero map_track[] on reset, then when the backend drivers get torn
down and release their mapping we hit the assert(s->map_track[ref] != 0)
in gnt_unref().
So leave them in place. Each backend driver will disconnect and reconnect
as the guest comes back up again and reconnects, and it all works out OK
in the end as the old refs get dropped.
Cc: qemu-stable@nongnu.org
Fixes: de26b26197 ("hw/xen: Implement soft reset for emulated gnttab")
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
This is only part of it; we will also need to get the PV back end drivers
to tear down their own mappings (or do it for them, but they kind of need
to stop using the pointers too).
Some more work on the actual PV back ends and xen-bus code is going to be
needed to really make soft reset and migration fully functional, and this
part is the basis for that.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
This is limited to mapping a single grant at a time, because under Xen the
pages are mapped *contiguously* into qemu's address space, and that's very
hard to do when those pages actually come from anonymous mappings in qemu
in the first place.
Eventually perhaps we can look at using shared mappings of actual objects
for system RAM, and then we can make new mappings of the same backing
store (be it deleted files, shmem, whatever). But for now let's stick to
a page at a time.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
