Re: [Xen-devel] RTC patch

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 22.08.12 at 12:48, Christoph Egger <Christoph.Egger@xxxxxxx> wrote:
> On 08/21/12 15:57, Jan Beulich wrote:
> 
>>>>> On 21.08.12 at 15:28, Christoph Egger <Christoph.Egger@xxxxxxx> wrote:
>>> On 08/20/12 13:06, Jan Beulich wrote:
>>>
>>>>>>> On 20.08.12 at 11:17, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
>>>>>     * fix high change rate to CMOS RTC periodic interrupt causing
>>>>>       guest wall clock time to lag (possible fix outlined, needs to be
>>>>>       put in patch form and thoroughly reviewed/tested for unwanted
>>>>>       side effects, Jan Beulich)
>>>>
>>>> Patch was posted, but no comments or approval to commit so far.
>>>> Also, reportedly the patch only improves the situation, it doesn't
>>>> completely eliminate the problem. For the moment I'm out of ideas,
>>>> though, and hence would hope some others could help here.
>>>
>>>
>>> Can you point me to the patch (or resend it to me), please?
>>> I have some trouble with getting XP Mode in Windows 7 (nested
>>> virtualization) booting and figured out it uses the RTC.
>>> I want to give this patch a try.
>> 
>> http://lists.xen.org/archives/html/xen-devel/2012-08/msg01303.html 
> 
> When booting Windows 7 I get a crash due to a NULL pointer dereference
> in xen/common/spinlock.c:45.
> It looks like the spin lock is not initialized.

I rather think NULL gets passed from pt_update_irq() to
rtc_periodic_interrupt(). Yet rtc.c's sole call to
create_periodic_time() clearly passes non-NULL. Oh,
hpet_set_timer() can pass a literal 8 (which I didn't spot
grepping for RTC_IRQ) - could you refine the check in
pt_update_irq()

    else if ( irq == RTC_IRQ )

to read

    else if ( irq == RTC_IRQ && pt_priv )

Jan


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