Re: [RFC] qemu: simulate edge-triggered interrupt in master PIC for time-drift-fix

[Dor Laor <dor.laor-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

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Carlo Marcelo Arenas Belon wrote:
> wrong patch, this was meant to go to the slave PIC, so it will use s->pics[1]
> instead of s->pics[0].
>
>   
Why to the slave pic? Isn't the pit connected to line 0 of the master?
> also from my tests it might seem that tdf is irrelevant anyway with the new
> clock work and haven't been able to find a case where enabling it (so
> triggering this buggy code path) migh be needed.
>
> any one care to comment on any current users of tdf? and if there are none in
> the viability for removing it?
>
>   
It does work but only for non-acpi guest that has the -no-kvm-irqchip 
parameter.
To test it you can load your host and see what happens to the clock when 
you run
a 1000HZ guest (use taskset to pin the guest with other cpu intensive 
tasks.)
We decided not to fix it in the in-kernel pic since once the tpr 
optimization enable
running acpi/apic guests and thus the pic is not used as time source.
Dor.
> Carlo
>
> On Fri, Nov 09, 2007 at 11:22:10AM -0600, Carlo Marcelo Arenas Belon wrote:
>   
>> The following patch fixes 1a483ef4040ed380bf69d684783d06a617073256 so that the
>> parent PIC pointer is used to send the edge irq0 instead of the PIC pair and
>> that is an incompatible pointer type as reported in :
>>
>> /var/tmp/portage/app-emulation/kvm-51/work/kvm-51/qemu/hw/i8259.c: In function
>> `
>> pic_read_irq':
>> /var/tmp/portage/app-emulation/kvm-51/work/kvm-51/qemu/hw/i8259.c:248:
>> warning: passing arg 1 of `pic_set_irq1' from incompatible pointer type
>> /var/tmp/portage/app-emulation/kvm-51/work/kvm-51/qemu/hw/i8259.c:249:
>> warning: passing arg 1 of `pic_set_irq1' from incompatible pointer type
>>
>> Signed-off-by: Carlo Marcelo Arenas Belon <carenas-kLeDWSohozoJb6fo7hG9ng@public.gmane.org>
>> ---
>>  qemu/hw/i8259.c |    4 ++--
>>  1 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/qemu/hw/i8259.c b/qemu/hw/i8259.c
>> index 01447d7..60063d4 100644
>> --- a/qemu/hw/i8259.c
>> +++ b/qemu/hw/i8259.c
>> @@ -245,8 +245,8 @@ int pic_read_irq(PicState2 *s)
>>  	    if (timer_ints_to_push > 0) {
>>  		timer_ints_to_push--;
>>                  /* simulate an edge irq0, like the one generated by i8254 */
>> -                pic_set_irq1(s, 0, 0);
>> -                pic_set_irq1(s, 0, 1);
>> +                pic_set_irq1(&s->pics[0], 0, 0);
>> +                pic_set_irq1(&s->pics[0], 0, 1);
>>  	    }
>>  	}
>>  
>> -- 
>> 1.5.2.5
>>
>>     
>
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