[Qemu-devel] Re: [PATCH 4/6] provide in-kernel i8259 chip

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

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Juan Quintela wrote:
> Glauber Costa <glommer@redhat.com> wrote:
>> On Tue, Sep 29, 2009 at 12:04:54AM +0200, Juan Quintela wrote:
>>> Glauber Costa <glommer@redhat.com> wrote:
>>>> This patch provides kvm with an in-kernel i8259 chip. We are currently not enabling it.
>>>> The code is heavily based on what's in qemu-kvm.git.
>>>>
>>>> Signed-off-by: Glauber Costa <glommer@redhat.com>
>>>> ---
>>>>  hw/i8259.c |  103 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>>>  hw/pc.h    |    1 +
>>>>  kvm-all.c  |   24 ++++++++++++++
>>>>  kvm.h      |    2 +
>>>>  4 files changed, 130 insertions(+), 0 deletions(-)
>>>>
>>>> diff --git a/hw/i8259.c b/hw/i8259.c
>>>> index 3de22e3..31524f5 100644
>>>> --- a/hw/i8259.c
>>>> +++ b/hw/i8259.c
>>>> @@ -26,6 +26,7 @@
>>>>  #include "isa.h"
>>>>  #include "monitor.h"
>>>>  #include "qemu-timer.h"
>>>> +#include "kvm.h"
>>>>  
>>>>  /* debug PIC */
>>>>  //#define DEBUG_PIC
>>>> @@ -446,9 +447,77 @@ static uint32_t elcr_ioport_read(void *opaque, uint32_t addr1)
>>>>      return s->elcr;
>>>>  }
>>>>  
>>>> +static int kvm_kernel_pic_load_from_user(void *opaque)
>>>> +{
>>>> +#if defined(TARGET_I386)
>>>> +    PicState *s = (void *)opaque;
>>>> +    struct kvm_irqchip chip;
>>>> +    struct kvm_pic_state *kpic;
>>> It miss:
>>>    if (!kvm_enabled() && !kvm_irqchip_enabled()) {
>>>       return 0;
>>>    }
>>>
>>> Or similar logic, otherwise kvm_set_irqchip() is called when kvm_irqchip
>>> is not enabled.  Same for save_to_user.
>>>
>>>> +    chip.chip_id = (&s->pics_state->pics[0] == s) ?
>>>> +                   KVM_IRQCHIP_PIC_MASTER :
>>>> +                   KVM_IRQCHIP_PIC_SLAVE;
>>>> +    kpic = &chip.chip.pic;
>>>> +
>>>> +    kpic->last_irr = s->last_irr;
>>>> +    kpic->irr = s->irr;
>>>> +    kpic->imr = s->imr;
>>>> +    kpic->isr = s->isr;
>>>> +    kpic->priority_add = s->priority_add;
>>>> +    kpic->irq_base = s->irq_base;
>>>> +    kpic->read_reg_select = s->read_reg_select;
>>>> +    kpic->poll = s->poll;
>>>> +    kpic->special_mask = s->special_mask;
>>>> +    kpic->init_state = s->init_state;
>>>> +    kpic->auto_eoi = s->auto_eoi;
>>>> +    kpic->rotate_on_auto_eoi = s->rotate_on_auto_eoi;
>>>> +    kpic->special_fully_nested_mode = s->special_fully_nested_mode;
>>>> +    kpic->init4 = s->init4;
>>>> +    kpic->elcr = s->elcr;
>>>> +    kpic->elcr_mask = s->elcr_mask;
>>>> +
>>>> +    kvm_set_irqchip(&chip);
>>>> +#endif
>>>> +    return 0;
>>>> +}
>>> ....
>>>>  static const VMStateDescription vmstate_pic = {
>>>>      .name = "i8259",
>>>>      .version_id = 1,
>>>> +    .pre_save = kvm_kernel_pic_save_to_user,
>>>> +    .post_load = kvm_kernel_pic_load_from_user,
>>> Let the three version_id fields together, please.
>>>
>>>
>>>> +#if defined(KVM_CAP_IRQCHIP) && defined(TARGET_I386)
>>>> +static void kvm_i8259_set_irq(void *opaque, int irq, int level)
>>>> +{
>>>> +    int pic_ret;
>>>> +    if (kvm_set_irq(irq, level, &pic_ret)) {
>>>> +        if (pic_ret != 0)
>>>> +            apic_set_irq_delivered();
>>>> +        return;
>>>> +    }
>>>> +}
>>>> +
>>>> +static void kvm_pic_init1(int io_addr, PicState *s)
>>>> +{
>>>> +    vmstate_register(io_addr, &vmstate_pic, s);
>>>> +    qemu_register_reset(pic_reset, s);
>>>> +}
>>>> +
>>>> +qemu_irq *kvm_i8259_init(qemu_irq parent_irq)
>>>> +{
>>>> +    PicState2 *s;
>>>> +
>>>> +    s = qemu_mallocz(sizeof(PicState2));
>>>> +
>>>> +    kvm_pic_init1(0x20, &s->pics[0]);
>>>> +    kvm_pic_init1(0xa0, &s->pics[1]);
>>>> +    s->parent_irq = parent_irq;
>>>> +    s->pics[0].pics_state = s;
>>>> +    s->pics[1].pics_state = s;
>>>> +    isa_pic = s;
>>>> +    return qemu_allocate_irqs(kvm_i8259_set_irq, s, 24);
>>>> +}
>>>> +#endif
>>> I think everything would be nicer if this three functions where merged
>>> with the _non_ kvm ones with a kvm_enable() test.  They only differ in
>>> 2-3 lines.
>> I disagree. I think it is a better solution long term to provide irqchips
>> that are completely free of kvm code.
> 
> Solutions:
> - you copy the file and lives synchronizing the changes
> - you export the needed funtions and then implement in the other file
>   the kvm bits.
> - you merge the kvm and non kvm bits.
> 
> I see here a very bad mix :(  The error showed before is due to the bad mix.
> 
> I showed 1 error, 1 question of style and 1 suggestion, you only
> answered to the suggestion.
> 
> Later, Juan.
> 

I agree with Juan here. And I would recommend to go the second path:
factor out shared code, e.g. into apic_common.c, and implement the
different variants in different files, maybe even as separate qdev
devices. The current situation is fairly unfortunate IMO.

Jan


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