Re: [Qemu-devel] [PATCH v3 1/5] hpet 'driftfix': add hooks required to detect coalesced interrupts (x86 apic only)

[Blue Swirl <blauwirbel@gmail.com>]

On Thu, Apr 28, 2011 at 5:24 PM, Ulrich Obergfell <uobergfe@redhat.com> wrote:
> 'target_get_irq_delivered' and 'target_reset_irq_delivered' contain
> entry addresses of functions that are utilized by update_irq() to
> detect coalesced interrupts. apic code loads these pointers during
> initialization.

I'm not so happy with this approach, but probably then the i386
dependencies can be removed from RTC and it can be compiled only once
for all targets.

> This change can be replaced if a generic feedback infrastructure to
> track coalesced IRQs for periodic, clock providing devices becomes
> available.
>
> Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
> ---
>  hw/apic.c |    4 ++++
>  sysemu.h  |    3 +++
>  vl.c      |    3 +++
>  3 files changed, 10 insertions(+), 0 deletions(-)
>
> diff --git a/hw/apic.c b/hw/apic.c
> index a45b57f..eb0f6d9 100644
> --- a/hw/apic.c
> +++ b/hw/apic.c
> @@ -24,6 +24,7 @@
>  #include "sysbus.h"
>  #include "trace.h"
>  #include "kvm.h"
> +#include "sysemu.h"
>
>  /* APIC Local Vector Table */
>  #define APIC_LVT_TIMER   0
> @@ -1143,6 +1144,9 @@ static SysBusDeviceInfo apic_info = {
>
>  static void apic_register_devices(void)
>  {
> +    target_get_irq_delivered = apic_get_irq_delivered;
> +    target_reset_irq_delivered = apic_reset_irq_delivered;
> +
>     sysbus_register_withprop(&apic_info);
>  }
>
> diff --git a/sysemu.h b/sysemu.h
> index 07d85cd..75b0139 100644
> --- a/sysemu.h
> +++ b/sysemu.h
> @@ -98,6 +98,9 @@ int qemu_savevm_state_complete(Monitor *mon, QEMUFile *f);
>  void qemu_savevm_state_cancel(Monitor *mon, QEMUFile *f);
>  int qemu_loadvm_state(QEMUFile *f);
>
> +extern int (*target_get_irq_delivered)(void);
> +extern void (*target_reset_irq_delivered)(void);
> +
>  /* SLIRP */
>  void do_info_slirp(Monitor *mon);
>
> diff --git a/vl.c b/vl.c
> index 0c24e07..7bab315 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -233,6 +233,9 @@ const char *prom_envs[MAX_PROM_ENVS];
>  const char *nvram = NULL;
>  int boot_menu;
>
> +int (*target_get_irq_delivered)(void) = 0;
> +void (*target_reset_irq_delivered)(void) = 0;

Instead of initializing with 0 (should be actually NULL in C), please
define stub functions, which are used by default. Then the users don't
need to check for NULL pointers.