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

[Jan Kiszka <jan.kiszka@web.de>]

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On 2011-01-26 14:08, Stefan Berger wrote:
> On 01/26/2011 07:09 AM, Jan Kiszka wrote:
>> 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?
>>
> The use case is to add a TPM device interface.
> 
> http://xenbits.xensource.com/xen-unstable.hg?file/1e56ac73b9b9/tools/ioemu/hw/tpm_tis.c
> 
> 
> This one typically is connected to the LPC bus.

I see. Do you also have the xen-free version of it? Maybe there are
still issues with proper qdev integration etc.

Jan


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