Re: [PATCH v2 2/6] KVM: x86/pmu: Refactoring find_arch_event() to pmc_perf_hw_id()

[Paolo Bonzini]

On 12/9/21 04:52, Jim Mattson wrote:
> Why don't we just use PERF_TYPE_RAW for guest counters all of the
> time? What is the advantage of matching entries in a table so that we
> can use PERF_TYPE_HARDWARE?

In theory it's so that hosts without support for architectural PMU 
events can map the architectural PMU events to their own.  In practice, 
we can probably return early from intel_pmu_refresh if the host does not 
support X86_FEATURE_ARCH_PERFMON, because only the oldest Pentium 4 
toasters^Wprocessors probably have VMX but lack architectural PMU.

Paolo