Re: [Xen-devel] RTC patch

[Christoph Egger <Christoph.Egger@xxxxxxx>]

On 08/22/12 16:47, Jan Beulich wrote:

>>>> 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 )

Yes, Windows 7 boots with this change.

Christoph


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