Re: [Qemu-devel] [PATCH] Don't enable a HPET timer if HPET is disabled

[Paolo Bonzini <pbonzini@redhat.com>]

Il 26/03/2014 21:20, Matt Lupfer ha scritto:
> On 02/22/2014 02:01 AM, Paolo Bonzini wrote:
>> Il 22/02/2014 05:37, Matt Lupfer ha scritto:
>>> A HPET timer can be started when HPET is not yet
>>> enabled. This will not generate an interrupt
>>> to the guest, but causes problems when HPET is later
>>> enabled.
>>>
>>> A timer that is created and expires at least once before
>>> HPET is enabled will have an initialized comparator based
>>> on a hpet_offset of 0 (uninitialized). When HPET is
>>> enabled, hpet_set_timer() is called a second time, which
>>> modifies the timer expiry to a time based on the
>>> difference between current ticks (measured with the
>>> newly initialized hpet_offset) and the timer's
>>> comparator (which was generated before hpet_offset was
>>> initialized). This results in a long period of no HPET
>>> timer ticks.
>>>
>>> When this occurs with a CentOS 5.x guest, the guest
>>> may not receive timer interrupts during its narrow
>>> timer check window and panic on boot.
>>>
>>> Signed-off-by: Matt Lupfer <mlupfer@ddn.com>
>>> ---
>>>  hw/timer/hpet.c | 3 ++-
>>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/hw/timer/hpet.c b/hw/timer/hpet.c
>>> index 1264dfd..e15d6bc 100644
>>> --- a/hw/timer/hpet.c
>>> +++ b/hw/timer/hpet.c
>>> @@ -506,7 +506,8 @@ static void hpet_ram_write(void *opaque, hwaddr addr,
>>>                  timer->cmp = (uint32_t)timer->cmp;
>>>                  timer->period = (uint32_t)timer->period;
>>>              }
>>> -            if (activating_bit(old_val, new_val, HPET_TN_ENABLE)) {
>>> +            if (activating_bit(old_val, new_val, HPET_TN_ENABLE) &&
>>> +                hpet_enabled(s)) {
>>>                  hpet_set_timer(timer);
>>>              } else if (deactivating_bit(old_val, new_val, HPET_TN_ENABLE)) {
>>>                  hpet_del_timer(timer);
>>>
>>
>> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
>
> Ping?  Now that 1.7.1 is out, I hope this small patch will be considered
> for the 2.0 release.
>
> http://patchwork.ozlabs.org/patch/323121/

Oops.  Michael, can you take care of this one?

Paolo