Re: [PATCH v2 4/4] KVM: x86/vPMU: Add lazy mechanism to release perf_event per vPMC

[Paolo Bonzini]

On 21/10/19 16:04, Like Xu wrote:
> 
>>
>> 2) introduce a new callback msr_idx_to_pmc that returns a struct
>> kvm_pmc*, and change kvm_pmu_is_valid_msr to do
> 
> For callback msr_idx_to_pmc,
> how do we deal with the input 'MSR_CORE_PERF_FIXED_CTR_CTRL'
> which may return several fixed kvm_pmcs not just one?

For RDMSR, do not do anything.  For WRMSR, you can handle it in the
set_msr callback.

>>
>> static int kvm_pmu_mark_pmc_in_use(struct kvm_vcpu *vcpu, u32 msr)
> 
> s/static int/static void/.
> 
>> {
>>     struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
>>     struct kvm_pmc *pmc = kvm_x86_ops->pmu_ops->msr_idx_to_pmc(vcpu, msr);
> 
> We need 'if(pmc)' here.

Agreed, sorry for the sloppiness.  Never interpret my suggestions as
more than pseudocode. :)

Paolo