When the HPET enters legacy mode, the IRQ output of the PIT is
suppressed and replaced by the HPET timer 0. But the current code to
emulate this was broken in many ways. It reset the PIT state after
re-enabling, it worked against a stale static PIT structure, and it did
not properly saved/restored the IRQ output mask in the PIT vmstate.
This patch solves the PIT IRQ control in a different way. On x86, it
both redirects the PIT IRQ to the HPET, just like the RTC. But it also
keeps the control line from the HPET to the PIT. This allows to disable
the PIT QEMU timer when it is not needed. The PIT's view on the control
line state is now saved in the same format that qemu-kvm is already
using.
Note that, in contrast to the suppressed RTC IRQ line, we do not need to
save/restore the PIT line state in the HPET. As we trigger a PIT IRQ
update via the control line, the line state is reconstructed on mode
switch.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
HPET legacy emulation will require control over the PIT IRQ output. To
enable this, add support for an alternative IRQ output object to the PIT
factory function. If the isa_irq number is < 0, this object will be
used.
This also removes the IRQ number property from the PIT class as we now
use a generic GPIO output pin that is connected by the factory function.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Move the public interface of the PIT into its own header file and update
all users.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Jan Kiszka