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

[Blue Swirl]

On Mon, Oct 1, 2012 at 4:20 PM, Anthony Liguori <address@hidden> wrote:
> Jan Kiszka <address@hidden> 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 <address@hidden>
>> ---
>>  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 <address@hidden>
>
> Blue/Aurelien, any objections?

No, maybe a message could be printed that says that the default has
changed, for a few releases.

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