[libvirt] [PATCHv4 1/4] vcpupin: inroduce a new libvir API (virDomainPinVcpuFlags)

[Adam Litke]

On 05/20/2011 05:17 PM, Eric Blake wrote:
> On 05/20/2011 02:54 PM, Adam Litke wrote:
>> I am really confused about what the default flags
>> (VIR_DOMAIN_VCPU_CURRENT) actually means.  It doesn't seem like I can
>> ever know what it means from an API perspective (since it's behavior is
>> arbitrary depending on the hypervisor).  Wouldn't it be better to
>> require _either_ VIR_DOMAIN_VCPU_LIVE _or_ VIR_DOMAIN_VCPU_CONFIG to be
>> set so that the intended behavior can be set with specificity?
> 
> Anywhere we use _CURRENT, it is supposed to mean _LIVE (if the VM is
> running) or _CONFIG (if the VM is persistent but offline).
> 
> Yes, explicitly specifying _LIVE, _CONFIG, or the combination of both,
> is probably better.
> 
> And in the past, we haven't always used those conventions; that is,
> there are some APIs where _CURRENT is non-zero, and the default (0) was
> unclear in its meaning.  But all new APIs should use _CURRENT as 0, so
> that the default has clear semantics.
> 
> However, there are some hypervisors that cannot do just _LIVE on
> persistent domains - they can only do _LIVE|_CONFIG (for transient
> domains, though, it should be obvious that just _LIVE works, since
> _CONFIG cannot succeed on a transient domain).
> 

Thanks for your explanation, Eric.  It's a lot clearer to me now and the
API makes sense.  Cleanups to the virsh documentation as you suggest
will hopefully prevent future questions like mine.

-- 
Adam Litke
IBM Linux Technology Center