Re: [PATCH 0/3] KVM: s390: Trace events support.

[Avi Kivity <avi@redhat.com>]

On 07/26/2012 01:47 PM, Cornelia Huck wrote:
> On Thu, 26 Jul 2012 12:35:10 +0300
> Avi Kivity <avi@redhat.com> wrote:
> 
>> On 07/23/2012 06:20 PM, Cornelia Huck wrote:
>> > Avi, Marcelo,
>> > 
>> > here's a patch set that introduces trace events for kvm/s390.
>> > 
>> > It's split into two parts:
>> > 
>> > - Trace points for architecture-defined events, like intercepts.
>> >   This patch calls into the disassembler via the interface provided
>> >   by the first patch. These trace points show up under events/kvm/.
>> > - Trace points for implementation-specific events like interrupt
>> >   injection. These show up under a new trace system, kvm-s390.
>> 
>> I don't see what's the difference between the two types.  Isn't
>> interrupt injection architectural?
> 
> I don't think so. The details how we do that might change, it's nothing
> dictated by the architecture.
> 
> (It might be argued where interrupt delivery belongs, since parts of it
> are architectured, while other parts are made up by us.)
> 
>> 
>> On x86, the implementation tracepoints are ones that may go away if the
>> implementation changes significantly, while the architectural ones will
>> not go away unless the architecture is changed.  
> 
> That's what I tried to do here as well.
> 
>> In fact creation and
>> destruction of vcpus and reset requests are not only architectural,
>> they're generic, you may as well add them to the arch independent trace
>> code.
> 
> The vpcu creation event also traces interesting information like the
> location of our sie control block (in fact, that's the most interesting
> information provided by the event).
> 
> The reset request traced is s390 specific (for diag 308 ipl).
> 
>> 
>> btw - why are vcpu creation and destruction useful events to trace?
> 
> See above - mainly for the control block location.

Ok, thanks for the explanations.  Applied all.


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