On Mon, Dec 03, 2018 at 02:31:14PM +0000, Will Deacon wrote:
> On Thu, Nov 22, 2018 at 11:25:48AM +0000, Andrew Murray wrote:
> > In order to effeciently enable/disable guest/host only perf counters
> > at guest entry/exit we add bitfields to kvm_cpu_context for guest and
> > host only events as well as accessors for updating them.
> >
> > Signed-off-by: Andrew Murray <[email protected]>
> > ---
> > arch/arm64/include/asm/kvm_host.h | 20 ++++++++++++++++++++
> > 1 file changed, 20 insertions(+)
> >
> > diff --git a/arch/arm64/include/asm/kvm_host.h
> > b/arch/arm64/include/asm/kvm_host.h
> > index 1550192..4a828eb 100644
> > --- a/arch/arm64/include/asm/kvm_host.h
> > +++ b/arch/arm64/include/asm/kvm_host.h
> > @@ -203,6 +203,8 @@ struct kvm_cpu_context {
> > };
> >
> > struct kvm_vcpu *__hyp_running_vcpu;
> > + u32 events_host_only;
> > + u32 events_guest_only;
> > };
> >
> > typedef struct kvm_cpu_context kvm_cpu_context_t;
> > @@ -472,6 +474,24 @@ static inline int kvm_arch_vcpu_run_pid_change(struct
> > kvm_vcpu *vcpu)
> > {
> > return kvm_arch_vcpu_run_map_fp(vcpu);
> > }
> > +static inline void kvm_clr_set_host_pmu_events(u32 clr, u32 set)
> > +{
> > + kvm_cpu_context_t *ctx = this_cpu_ptr(&kvm_host_cpu_state);
> > +
> > + ctx->events_host_only &= ~clr;
> > + ctx->events_host_only |= set;
> > +}
>
> Do you actually need this clr/set function, or can you just use the
> facilities provided by bitfield.h at the callsites?
This modifies events_{host|guest}_only which is conditionally defined
(CONFIG_KVM) yet used by arch/arm64/kernel/perf_events which is also
conditionally defined (CONFIG_HW_PERF_EVENTS). By moving this away
from the callsite we avoid a load of horrible #ifdef's and allow this
function to become a nop when KVM isn't enabled.
Is there value in updating this function to use set_bit/clear_bit
functions in bitops/atomic.h ?
Andrew Murray
>
> Will
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