Re: [Qemu-devel] [PATCH] kvm: Set default accelerator to "kvm" if the host supports it

[Anthony Liguori <anthony@codemonkey.ws>]

Jan Kiszka <jan.kiszka@siemens.com> writes:

> If we built a target for a host that supports KVM in principle, set the
> default accelerator to KVM as well. This also means the start of QEMU
> will fail to start if KVM support turns out to be unavailable at
> runtime.
>
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> ---
>  kvm-all.c  |    1 +
>  kvm-stub.c |    1 +
>  kvm.h      |    1 +
>  vl.c       |    4 ++--
>  4 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/kvm-all.c b/kvm-all.c
> index 92a7137..4d5f86c 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -103,6 +103,7 @@ struct KVMState
>  #endif
>  };
>  
> +bool kvm_configured = true;
>  KVMState *kvm_state;
>  bool kvm_kernel_irqchip;
>  bool kvm_async_interrupts_allowed;
> diff --git a/kvm-stub.c b/kvm-stub.c
> index 3c52eb5..86a6451 100644
> --- a/kvm-stub.c
> +++ b/kvm-stub.c
> @@ -17,6 +17,7 @@
>  #include "gdbstub.h"
>  #include "kvm.h"
>  
> +bool kvm_configured;
>  KVMState *kvm_state;
>  bool kvm_kernel_irqchip;
>  bool kvm_async_interrupts_allowed;
> diff --git a/kvm.h b/kvm.h
> index dea2998..9936e5f 100644
> --- a/kvm.h
> +++ b/kvm.h
> @@ -22,6 +22,7 @@
>  #include <linux/kvm.h>
>  #endif
>  
> +extern bool kvm_configured;
>  extern int kvm_allowed;
>  extern bool kvm_kernel_irqchip;
>  extern bool kvm_async_interrupts_allowed;
> diff --git a/vl.c b/vl.c
> index 8d305ca..f557bd1 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -2215,8 +2215,8 @@ static int configure_accelerator(void)
>      }
>  
>      if (p == NULL) {
> -        /* Use the default "accelerator", tcg */
> -        p = "tcg";
> +        /* The default accelerator depends on the availability of KVM. */
> +        p = kvm_configured ? "kvm" : "tcg";
>      }

How about making this an arch_init() function call and then using a #if
defined(KVM_CONFIG) in arch_init.c?

I hate to introduce another global variable if we can avoid it...

Otherwise:

Acked-by: Anthony Liguori <aliguori@us.ibm.com>

Blue/Aurelien, any objections?

Regards,

Anthony Liguori

>  
>      while (!accel_initialised && *p != '\0') {
> -- 
> 1.7.3.4