commit 369b41359a broke timer interrupt
reinjection when there is no period change by the guest.
In that case, old_period is 0, which ends up zeroing irq_coalesced
(counter of reinjected interrupts).
The consequence is Windows 7 is unable to synchronize time via NTP.
Easily reproducible by playing a fullscreen video with cirrus and VNC.
Fix by not updating s->irq_coalesced when old_period is 0.
V2: reorganize code (Paolo Bonzini)
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Message-Id: <20191010123008.GA19158@amt.cnet>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
b429de7301