Re: [Qemu-devel] Re: Errors on MMIO read access on VM suspend / resume operations

[Jan Kiszka]

On 2011-01-26 13:05, Stefan Berger wrote:
> On 01/26/2011 03:14 AM, Jan Kiszka wrote:
>> On 2011-01-25 17:49, Stefan Berger wrote:
>>> On 01/25/2011 02:26 AM, Jan Kiszka wrote:
>>>> Do you see a chance to look closer at the issue yourself? E.g.
>>>> instrument the kernel's irqchip models and dump their states once your
>>>> guest is stuck?
>>> The device runs on iRQ 3. So I applied this patch here.
>>>
>>> diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
>>> index 3cece05..8f4f94c 100644
>>> --- a/arch/x86/kvm/i8259.c
>>> +++ b/arch/x86/kvm/i8259.c
>>> @@ -106,7 +106,7 @@ static inline int pic_set_irq1(struct kvm_kpic_state
>>> *s, int irq, int level)
>>>   {
>>>       int mask, ret = 1;
>>>       mask = 1<<   irq;
>>> -    if (s->elcr&   mask)    /* level triggered */
>>> +    if (s->elcr&   mask)    /* level triggered */ {
>>>           if (level) {
>>>               ret = !(s->irr&   mask);
>>>               s->irr |= mask;
>>> @@ -115,7 +115,10 @@ static inline int pic_set_irq1(struct
>>> kvm_kpic_state *s, int irq, int level)
>>>               s->irr&= ~mask;
>>>               s->last_irr&= ~mask;
>>>           }
>>> -    else    /* edge triggered */
>>> +if (irq == 3)
>>> +    printk("%s %d: level=%d, irr = %x\n", __FUNCTION__,__LINE__,level,
>>> s->irr);
>>> +        }
>>> +    else    /* edge triggered */ {
>>>           if (level) {
>>>               if ((s->last_irr&   mask) == 0) {
>>>                   ret = !(s->irr&   mask);
>>> @@ -124,7 +127,9 @@ static inline int pic_set_irq1(struct kvm_kpic_state
>>> *s, int irq, int level)
>>>               s->last_irr |= mask;
>>>           } else
>>>               s->last_irr&= ~mask;
>>> -
>>> +if (irq == 3)
>>> +    printk("%s %d: level=%d, irr = %x\n", __FUNCTION__,__LINE__,level,
>>> s->irr);
>>> +        }
>>>       return (s->imr&   mask) ? -1 : ret;
>>>   }
>>>
>>> @@ -206,6 +211,8 @@ int kvm_pic_set_irq(void *opaque, int irq, int
>>> level)
>>>
>>>       pic_lock(s);
>>>       if (irq>= 0&&   irq<   PIC_NUM_PINS) {
>>> +if (irq == 3)
>>> +printk("%s\n", __FUNCTION__);
>>>           ret = pic_set_irq1(&s->pics[irq>>   3], irq&   7, level);
>>>           pic_update_irq(s);
>>>           trace_kvm_pic_set_irq(irq>>   3, irq&   7, s->pics[irq>>  
>>> 3].elcr,
>>>
>>>
>>>
>>> While it's still working I see this here with the levels changing 0-1-0.
>>> Though then it stops and levels are only at '1'.
>>>
>>> [ 1773.833824] kvm_pic_set_irq
>>> [ 1773.833827] pic_set_irq1 131: level=0, irr = 5b
>>> [ 1773.834161] kvm_pic_set_irq
>>> [ 1773.834163] pic_set_irq1 131: level=1, irr = 5b
>>> [ 1773.834193] kvm_pic_set_irq
>>> [ 1773.834195] pic_set_irq1 131: level=0, irr = 5b
>>> [ 1773.835028] kvm_pic_set_irq
>>> [ 1773.835031] pic_set_irq1 131: level=1, irr = 5b
>>> [ 1773.835542] kvm_pic_set_irq
>>> [ 1773.835545] pic_set_irq1 131: level=1, irr = 5b
>>> [ 1773.889892] kvm_pic_set_irq
>>> [ 1773.889894] pic_set_irq1 131: level=1, irr = 5b
>>> [ 1791.258793] pic_set_irq1 119: level=1, irr = d9
>>> [ 1791.258824] pic_set_irq1 119: level=0, irr = d1
>>> [ 1791.402476] pic_set_irq1 119: level=1, irr = d9
>>> [ 1791.402534] pic_set_irq1 119: level=0, irr = d1
>>> [ 1791.402538] pic_set_irq1 119: level=1, irr = d9
>>> [...]
>>>
>>>
>>> I believe the last 5 shown calls can be ignored. After that the
>>> interrupts don't go through anymore.
>>>
>>> In the device model I see interrupts being raised and cleared. After the
>>> last one was cleared in 'my' device model, only interrupts are raised.
>>> This looks like as if the interrupt handler in the guest Linux was never
>>> run, thus the IRQ is never cleared and we're stuck.
>>>
>> User space is responsible for both setting and clearing that line. IRQ3
>> means you are using some serial device model? Then you should check what
>> its state is.
> Good hint. I moved it now to IRQ11 and it works fine now (with kvm-git)
> from what I can see. There was no UART on IRQ3 before, though, but
> certainly it was the wrong IRQ for it.
>> Moreover, a complete picture of the kernel/user space interaction should
>> be obtainable by using fstrace for capturing kvm events.
>>
> Should it be working on IRQ3? If so, I'd look into it when I get a
> chance...

I don't know your customizations, so it's hard to tell if that should
work or not. IRQ3 is intended to be used by ISA devices on the PC
machine. Are you adding an ISA model, or what is your use case?

Jan

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