On Mon, Dec 10, 2018 at 09:45:57AM +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 events as well as accessors for updating them.
>
> Signed-off-by: Andrew Murray <andrew.murray@xxxxxxx>
> ---
> arch/arm64/include/asm/kvm_host.h | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 1550192..800c87b 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;
> + u32 events_guest;
This is confusing to me.
These values appear only to be used for the host instance, which makes
me wonder why we add them to kvm_cpu_context, which is also used for the
guest state? Should we not instead consider moving them to their own
data structure and add a per-cpu data structure or something more fancy
like having a new data structure, kvm_percpu_host_data, which contains
the kvm_cpu_context and the events flags?
I don't know much about perf, but doesn't this design also imply that
you can only set these modifiers at a per-cpu level, and not attach
the modifiers to a task/vcpu or vm ? Is that by design?
Thanks,
Christoffer
> };
>
> typedef struct kvm_cpu_context kvm_cpu_context_t;
> @@ -467,11 +469,33 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu);
> void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu);
> void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu);
>
> +#define KVM_PMU_EVENTS_HOST 1
> +#define KVM_PMU_EVENTS_GUEST 2
> +
> #ifdef CONFIG_KVM /* Avoid conflicts with core headers if CONFIG_KVM=n */
> 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_set_pmu_events(u32 set, int flags)
> +{
> + kvm_cpu_context_t *ctx = this_cpu_ptr(&kvm_host_cpu_state);
> +
> + if (flags & KVM_PMU_EVENTS_HOST)
> + ctx->events_host |= set;
> + if (flags & KVM_PMU_EVENTS_GUEST)
> + ctx->events_guest |= set;
> +}
> +static inline void kvm_clr_pmu_events(u32 clr)
> +{
> + kvm_cpu_context_t *ctx = this_cpu_ptr(&kvm_host_cpu_state);
> +
> + ctx->events_host &= ~clr;
> + ctx->events_guest &= ~clr;
> +}
> +#else
> +static inline void kvm_set_pmu_events(u32 set, int flags) {}
> +static inline void kvm_clr_pmu_events(u32 clr) {}
> #endif
>
> static inline void kvm_arm_vhe_guest_enter(void)
> --
> 2.7.4
>
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