[Qemu-devel] Interrupt request info

[Qemu-devel] Interrupt request info

[Alessandro Corradi]

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Hello,
Can someone give me detailed information (or a link where it is described)
how qemu manage hw interrupts?
I can't find any usefull info about it in QEMU doc.
For example, how does work Interrupts for the parallel port? (I see in the
code that it is the easier device to understand how qemu works).
I think that it is very usefull for students and newbies to have more
detailed documentations about it for understanding
virtualizzation/emulation.

Thank you very much
Ale

ps: Obviously, if these information are already present I apologize me in
advance, I try to search but nothing was found  :)

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Re: [Qemu-devel] Interrupt request info

[Rob Landley]

On Saturday 28 October 2006 5:36 am, Alessandro Corradi wrote:
> Hello,
> Can someone give me detailed information (or a link where it is described)
> how qemu manage hw interrupts?
> I can't find any usefull info about it in QEMU doc.

http://www.qemu.org/qemu-tech.html#SEC18

> ps: Obviously, if these information are already present I apologize me in
> advance, I try to search but nothing was found  :)

The documentation is a bit sparse in places.

Rob
-- 
"Perfection is reached, not when there is no longer anything to add, but
when there is no longer anything to take away." - Antoine de Saint-Exupery

Fwd: [Qemu-devel] Interrupt request info

[Alessandro Corradi]

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---------- Forwarded message ----------
From: Alessandro Corradi <ale.corradi@gmail.com>
Date: 31-ott-2006 10.25
Subject: Re: [Qemu-devel] Interrupt request info
To: Rob Landley <rob@landley.net>

I already read this, but give no usefull information... and I searched
everywhere in the web...
For example, I wrote a module of a simple memory without implementing IRQ...
I think it is  an error but it works fine... are IRQ raise in any case???
I look at other code source of implemented hw but for each device there is a
differeny way to raise an interrupt (i see).
Is there a standard way to do this?
The following is an excerpt of my simple memory, please can you describe me
fastly how can I manage this?

Thank you


struct scmemState {
    uint32_t data;
    uint32_t addr;
    uint32_t control;
    uint32_t comm;

    int irq;
    int irq_pending;
};

scmemState *scmem_init(int base, int irq){
    scmemState *s;

    s=qemu_mallocz(sizeof(scmemState));
    s->irq = irq;
    s->data = 0;
    s->addr = 0;
    s->control = 0;
    ...
}
static void scmem_ioport_write(void *opaque, uint32_t addr, uint32_t val) {
    scmemState *s = opaque;
    addr &= 7;
    switch(addr) {
    case 0:
        cosim(1,DATA,val);
        s->data = val;
        #ifdef SCDEBUG
        printf("Writing at 0x738 (data reg) value= %d\n",val);
        #endif
        break;
    case 1:
        cosim(1,ADDR,val);
        s->addr = val;
        #ifdef SCDEBUG
        printf("Writing at 0x739 (addr reg) value= %d\n",val);
        #endif
        break;
    case 2:
        cosim(1,CONTROL,val);
        s->control = val;
        #ifdef SCDEBUG
        printf("Writing at 0x74a (control reg) value= %d\n",val);
        #endif
        break;
    case 3:
        if (val == 0x0003) { //SC socket connection restore
            scmem_restore();
        } else {
            cosim(1,COMM,val);
            s->comm = val;
            #ifdef SCDEBUG
            printf("Writing at 0x74b (comm reg) value= %d\n",val);
            #endif
        }
        break;
    }
}


2006/10/28, Rob Landley < rob@landley.net >:
>
> On Saturday 28 October 2006 5:36 am, Alessandro Corradi wrote:
> > Hello,
> > Can someone give me detailed information (or a link where it is
> described)
> > how qemu manage hw interrupts?
> > I can't find any usefull info about it in QEMU doc.
>
> http://www.qemu.org/qemu-tech.html#SEC18
>
> > ps: Obviously, if these information are already present I apologize me
> in
> > advance, I try to search but nothing was found  :)
>
> The documentation is a bit sparse in places.
>
> Rob
> --
> "Perfection is reached, not when there is no longer anything to add, but
> when there is no longer anything to take away." - Antoine de Saint-Exupery
>

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Re: Fwd: [Qemu-devel] Interrupt request info

[Paul Brook]

> I already read this, but give no usefull information... and I searched
> everywhere in the web...
> For example, I wrote a module of a simple memory without implementing
> IRQ... I think it is  an error but it works fine... are IRQ raise in any
> case??? I look at other code source of implemented hw but for each device
> there is a differeny way to raise an interrupt (i see).
> Is there a standard way to do this?

pic_set_irq_new

Paul

Re:[Qemu-devel] Interrupt request info

[Roger Lathrop]

Alessandro,

All you should need to do to raise an IRQ in your code is:
pic_set_irq(s->irq,1);

When the irq is serviced (in one of your ioport traps, I would assume), 
knock the irq down:
pic_set_irq(s->irq,0);

For debugging, you might want to go into i8259.c and uncomment the #define 
DEBUG_IRQ_COUNT line.
You can then use command 'info irq' in the monitor console. This will show 
you a count of interrupts for each IRQ.

Regards,
Roger

> For example, I wrote a module of a simple memory without implementing 
> IRQ...
> I think it is  an error but it works fine... are IRQ raise in any case???
> I look at other code source of implemented hw but for each device there is 
> a
> differeny way to raise an interrupt (i see).
> Is there a standard way to do this?
> The following is an excerpt of my simple memory, please can you describe 
> me
> fastly how can I manage this?
>
> Thank you

Re: [Qemu-devel] Interrupt request info

[Paul Brook]

On Wednesday 01 November 2006 23:25, Roger Lathrop wrote:
> Alessandro,
>
> All you should need to do to raise an IRQ in your code is:
> pic_set_irq(s->irq,1);
>
> When the irq is serviced (in one of your ioport traps, I would assume),
> knock the irq down:
> pic_set_irq(s->irq,0);

No. You should use pic_set_irq_new. Otherwise your code will break on machines 
with multiple interrupt controllers.

Paul

Re: [Qemu-devel] Interrupt request info

[Alessandro Corradi]

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Thank you very much for the answer,
so the only think to do to raise correctly an interrupt (I think) is only to
raise it when a read funciton is completed (in case of my simple memory)
because it will alarm the process in waiting status to read the value in the
register.

the workaround of a read operation of a cell of this memory is:
1)write address of the cell that I want to read in the address register,
2)send the execution request to get the value of the cell indicated by the
address reg (write on the command register the read opcode),
3)wait for control register response untill read operation is executed.
4)read the data register.

so I think that interrupt request must be between point 3 and 4.
Do you agree with my consideration?

I hope that writed something understandable :)

Thanks

Ale


2006/11/2, Paul Brook <paul@codesourcery.com>:
>
> On Wednesday 01 November 2006 23:25, Roger Lathrop wrote:
> > Alessandro,
> >
> > All you should need to do to raise an IRQ in your code is:
> > pic_set_irq(s->irq,1);
> >
> > When the irq is serviced (in one of your ioport traps, I would assume),
> > knock the irq down:
> > pic_set_irq(s->irq,0);
>
> No. You should use pic_set_irq_new. Otherwise your code will break on
> machines
> with multiple interrupt controllers.
>
> Paul
>
>
> _______________________________________________
> Qemu-devel mailing list
> Qemu-devel@nongnu.org
> http://lists.nongnu.org/mailman/listinfo/qemu-devel
>

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Re: [Qemu-devel] Interrupt request info

[Alessandro Corradi]

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Thank you very much,
But I don't understand what the first parameter is on pic_set_irq_new...
I tried anyway to implement my hw with pic_set_irq, but in qemu console I
didn't see my irq (13) with info irq.
I tried to raise it: pic_set_irq(s->irq,1);

What I need to do to raise irq correctly with pic_set_irq_new specially the
first parameter)?

Thank you

2006/11/2, Paul Brook <paul@codesourcery.com>:
>
> On Wednesday 01 November 2006 23:25, Roger Lathrop wrote:
> > Alessandro,
> >
> > All you should need to do to raise an IRQ in your code is:
> > pic_set_irq(s->irq,1);
> >
> > When the irq is serviced (in one of your ioport traps, I would assume),
> > knock the irq down:
> > pic_set_irq(s->irq,0);
>
> No. You should use pic_set_irq_new. Otherwise your code will break on
> machines
> with multiple interrupt controllers.
>
> Paul
>
>
> _______________________________________________
> Qemu-devel mailing list
> Qemu-devel@nongnu.org
> http://lists.nongnu.org/mailman/listinfo/qemu-devel
>

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Re: [Qemu-devel] Interrupt request info

[Alessandro Corradi]

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I tried with both pic_set_irq and pic_set_irq_new but nothing happen (the
irq number is 13 and I verified with info irq in qemu monitor).
I tried also to hack i8259.c and the function is not called (I think).
What the first parameter of pic_set_irq_new is referred to?

Another question: why a new virtual device works anyway without interrupt
mechanism? isn't it essential?

Thanks

Ale

2006/11/2, Paul Brook <paul@codesourcery.com>:
>
> On Wednesday 01 November 2006 23:25, Roger Lathrop wrote:
> > Alessandro,
> >
> > All you should need to do to raise an IRQ in your code is:
> > pic_set_irq(s->irq,1);
> >
> > When the irq is serviced (in one of your ioport traps, I would assume),
> > knock the irq down:
> > pic_set_irq(s->irq,0);
>
> No. You should use pic_set_irq_new. Otherwise your code will break on
> machines
> with multiple interrupt controllers.
>
> Paul
>
>
> _______________________________________________
> Qemu-devel mailing list
> Qemu-devel@nongnu.org
> http://lists.nongnu.org/mailman/listinfo/qemu-devel
>

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