Re: [Qemu-devel] [PATCH 2/9] kvm: add kvm_enable_cap_{vm,vcpu}

[Alexander Graf]

On 16.04.2014, at 13:22, Alexander Graf <address@hidden> wrote:

> 
> On 14.04.14 18:48, Cornelia Huck wrote:
>> Provide helper functions for enabling capabilities (on a vcpu and on a vm).
>> 
>> Reviewed-by: Thomas Huth <address@hidden>
>> Signed-off-by: Cornelia Huck <address@hidden>
>> ---
>>  include/sysemu/kvm.h |    4 ++++
>>  kvm-all.c            |   33 ++++++++++++++++++++++++++++++++-
>>  2 files changed, 36 insertions(+), 1 deletion(-)
>> 
>> diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
>> index 0bee1e8..2ff5ad3 100644
>> --- a/include/sysemu/kvm.h
>> +++ b/include/sysemu/kvm.h
>> @@ -294,6 +294,10 @@ bool kvm_arch_stop_on_emulation_error(CPUState *cpu);
>>    int kvm_check_extension(KVMState *s, unsigned int extension);
>>  +int kvm_enable_cap_vm(KVMState *s, unsigned int capability, ...);
>> +
>> +int kvm_enable_cap_vcpu(CPUState *cpu, unsigned int capability, ...);
>> +
>>  uint32_t kvm_arch_get_supported_cpuid(KVMState *env, uint32_t function,
>>                                        uint32_t index, int reg);
>>  diff --git a/kvm-all.c b/kvm-all.c
>> index cd4111d..658e50c 100644
>> --- a/kvm-all.c
>> +++ b/kvm-all.c
>> @@ -501,7 +501,38 @@ int kvm_check_extension(KVMState *s, unsigned int 
>> extension)
>>      return ret;
>>  }
>>  -static int kvm_set_ioeventfd_mmio(int fd, hwaddr addr, uint32_t val,
>> +int kvm_enable_cap_vm(KVMState *s, unsigned int capability, ...)
>> +{
>> +    struct kvm_enable_cap cap = {};
>> +    va_list ap;
>> +    int i;
>> +
>> +    cap.cap = capability;
>> +    va_start(ap, capability);
>> +    for (i = 0; i < 4; i++) {
>> +        cap.args[i] = va_arg(ap, uint64_t);
> 
> Is this legit? Can we just pull items off the stack without running beyond?

For inspiration on how to know the number of arguments that got passed in, 
check out

  http://git.qemu.org/?p=qemu.git;a=blob;f=include/sysemu/device_tree.h#l40


Alex