[1/6] kvm: Decouple 'interrupt injection is async' from 'kernel irqchip'

On x86 interrupt injection is asynchronous (and therefore
VCPU idle management is done in the kernel) if and only
if there is an in-kernel irqchip. On other architectures this
isn't necessarily true (they may always do asynchronous
injection), so define a new kvm_async_interrupt_injection()
function instead of misusing kvm_irqchip_in_kernel().

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 cpus.c     |    3 ++-
 kvm-all.c  |    7 ++++++-
 kvm-stub.c |    1 +
 kvm.h      |   11 +++++++++++
 4 files changed, 20 insertions(+), 2 deletions(-)

On 2012-07-25 15:24, Peter Maydell wrote:
> On x86 interrupt injection is asynchronous (and therefore
> VCPU idle management is done in the kernel) if and only
> if there is an in-kernel irqchip. On other architectures this
> isn't necessarily true (they may always do asynchronous
> injection), so define a new kvm_async_interrupt_injection()
> function instead of misusing kvm_irqchip_in_kernel().
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  cpus.c     |    3 ++-
>  kvm-all.c  |    7 ++++++-
>  kvm-stub.c |    1 +
>  kvm.h      |   11 +++++++++++
>  4 files changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/cpus.c b/cpus.c
> index 756e624..584b298 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -69,7 +69,8 @@ static bool cpu_thread_is_idle(CPUArchState *env)
>      if (env->stopped || !runstate_is_running()) {
>          return true;
>      }
> -    if (!env->halted || qemu_cpu_has_work(env) || kvm_irqchip_in_kernel()) {
> +    if (!env->halted || qemu_cpu_has_work(env) ||
> +        kvm_async_interrupt_injection()) {
>          return false;
>      }
>      return true;
> diff --git a/kvm-all.c b/kvm-all.c
> index 2148b20..3354c6f 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -100,6 +100,7 @@ struct KVMState
>  
>  KVMState *kvm_state;
>  bool kvm_kernel_irqchip;
> +bool kvm_async_interrupt_injection;
>  
>  static const KVMCapabilityInfo kvm_required_capabilites[] = {
>      KVM_CAP_INFO(USER_MEMORY),
> @@ -857,7 +858,7 @@ int kvm_irqchip_set_irq(KVMState *s, int irq, int level)
>      struct kvm_irq_level event;
>      int ret;
>  
> -    assert(kvm_irqchip_in_kernel());
> +    assert(kvm_async_interrupt_injection());
>  
>      event.level = level;
>      event.irq = irq;
> @@ -1201,6 +1202,10 @@ static int kvm_irqchip_create(KVMState *s)
>          s->irqchip_inject_ioctl = KVM_IRQ_LINE_STATUS;
>      }
>      kvm_kernel_irqchip = true;
> +    /* If we have an in-kernel IRQ chip then we must have asynchronous
> +     * interrupt injection (though the reverse is not necessarily true)
> +     */
> +    kvm_async_interrupt_injection = true;
>  
>      kvm_init_irq_routing(s);
>  
> diff --git a/kvm-stub.c b/kvm-stub.c
> index d23b11c..b4023d1 100644
> --- a/kvm-stub.c
> +++ b/kvm-stub.c
> @@ -19,6 +19,7 @@
>  
>  KVMState *kvm_state;
>  bool kvm_kernel_irqchip;
> +bool kvm_async_interrupt_injection;
>  
>  int kvm_init_vcpu(CPUArchState *env)
>  {
> diff --git a/kvm.h b/kvm.h
> index 2617dd5..00abe36 100644
> --- a/kvm.h
> +++ b/kvm.h
> @@ -24,13 +24,24 @@
>  
>  extern int kvm_allowed;
>  extern bool kvm_kernel_irqchip;
> +extern bool kvm_async_interrupt_injection;
>  
>  #if defined CONFIG_KVM || !defined NEED_CPU_H
>  #define kvm_enabled()           (kvm_allowed)
>  #define kvm_irqchip_in_kernel() (kvm_kernel_irqchip)
> +/**
> + * kvm_async_interrupt_injection:
> + *
> + * Returns: true if we can inject interrupts into a KVM CPU
> + * asynchronously (ie by ioctl from any thread at any time)
> + * rather than having to do interrupt delivery synchronously
> + * (where the vcpu must be stopped at a suitable point first).
> + */
> +#define kvm_async_interrupt_injection() (kvm_async_interrupt_injection)
>  #else
>  #define kvm_enabled()           (0)
>  #define kvm_irqchip_in_kernel() (false)
> +#define kvm_async_interrupt_injection() (false)
>  #endif
>  
>  struct kvm_run;
> 

Acked-by: Jan Kiszka <jan.kiszka@siemens.com>