Re: [PATCH v6 02/21] KVM: ARM64: Define PMU data structure for each vcpu

[Will Deacon <will.deacon@arm.com>]

On Tue, Dec 08, 2015 at 01:37:14PM +0000, Marc Zyngier wrote:
> On 08/12/15 12:47, Shannon Zhao wrote:
> > From: Shannon Zhao <shannon.zhao@linaro.org>
> > 
> > Here we plan to support virtual PMU for guest by full software
> > emulation, so define some basic structs and functions preparing for
> > futher steps. Define struct kvm_pmc for performance monitor counter and
> > struct kvm_pmu for performance monitor unit for each vcpu. According to
> > ARMv8 spec, the PMU contains at most 32(ARMV8_MAX_COUNTERS) counters.
> > 
> > Since this only supports ARM64 (or PMUv3), add a separate config symbol
> > for it.
> > 
> > Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
> > ---
> >  arch/arm64/include/asm/kvm_host.h |  2 ++
> >  arch/arm64/kvm/Kconfig            |  8 ++++++++
> >  include/kvm/arm_pmu.h             | 40 +++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 50 insertions(+)
> >  create mode 100644 include/kvm/arm_pmu.h

[...]

> > diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
> > index a5272c0..66da9a2 100644
> > --- a/arch/arm64/kvm/Kconfig
> > +++ b/arch/arm64/kvm/Kconfig
> > @@ -36,6 +36,7 @@ config KVM
> >  	select HAVE_KVM_EVENTFD
> >  	select HAVE_KVM_IRQFD
> >  	select KVM_ARM_VGIC_V3
> > +	select KVM_ARM_PMU
> 
> What if HW_PERF_EVENTS is not selected? Also, selecting HW_PERF_EVENTS
> is not enough, and you probably need PERF_EVENTS as well, So this should
> probably read:
> 
> 	select KVM_ARM_PMU if (HW_PERF_EVENTS && PERF_EVENTS)

HW_PERF_EVENTS depends on ARM_PMU which in turn depends on PERF_EVENTS.

Will