On Mon, Jan 14, 2019 at 04:11:48PM +0000, Andrew Murray wrote:
> Enable/disable event counters as appropriate when entering and exiting
> the guest to enable support for guest or host only event counting.
>
> For both VHE and non-VHE we switch the counters between host/guest at
> EL2. EL2 is filtered out by the PMU when we are using the :G modifier.
I don't think the last part is strictly true as per the former patch on
a non-vhe system if you have the :h modifier, so maybe just leave that
out of the commit message.
>
> The PMU may be on when we change which counters are enabled however
> we avoid adding an isb as we instead rely on existing context
> synchronisation events: the isb in kvm_arm_vhe_guest_exit for VHE and
> the eret from the hvc in kvm_call_hyp.
>
> Signed-off-by: Andrew Murray <andrew.murray at arm.com>
> Reviewed-by: Suzuki K Poulose <suzuki.poulose at arm.com>
> ---
> arch/arm64/kvm/hyp/switch.c | 60 +++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 60 insertions(+)
>
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index b0b1478..9018fb3 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -357,6 +357,54 @@ static bool __hyp_text __hyp_switch_fpsimd(struct kvm_vcpu *vcpu)
> return true;
> }
>
> +static bool __hyp_text __pmu_switch_to_guest(struct kvm_cpu_context *host_ctxt)
> +{
> + struct kvm_host_data *host;
> + struct kvm_pmu_events *pmu;
> + u32 clr, set;
> +
> + host = container_of(host_ctxt, struct kvm_host_data, host_ctxt);
> + pmu = &host->pmu_events;
> +
> + /* We can potentially avoid a sysreg write by only changing bits that
> + * differ between the guest/host. E.g. where events are enabled in
> + * both guest and host
> + */
super nit: kernel coding style requires 'wings' on both side of a
multi-line comment. Only if you respin anyhow.
> + clr = pmu->events_host & ~pmu->events_guest;
> + set = pmu->events_guest & ~pmu->events_host;
> +
> + if (clr)
> + write_sysreg(clr, pmcntenclr_el0);
> +
> + if (set)
> + write_sysreg(set, pmcntenset_el0);
> +
> + return (clr || set);
> +}
> +
> +static void __hyp_text __pmu_switch_to_host(struct kvm_cpu_context *host_ctxt)
> +{
> + struct kvm_host_data *host;
> + struct kvm_pmu_events *pmu;
> + u32 clr, set;
> +
> + host = container_of(host_ctxt, struct kvm_host_data, host_ctxt);
> + pmu = &host->pmu_events;
> +
> + /* We can potentially avoid a sysreg write by only changing bits that
> + * differ between the guest/host. E.g. where events are enabled in
> + * both guest and host
> + */
ditto
> + clr = pmu->events_guest & ~pmu->events_host;
> + set = pmu->events_host & ~pmu->events_guest;
> +
> + if (clr)
> + write_sysreg(clr, pmcntenclr_el0);
> +
> + if (set)
> + write_sysreg(set, pmcntenset_el0);
> +}
> +
> /*
> * Return true when we were able to fixup the guest exit and should return to
> * the guest, false when we should restore the host state and return to the
> @@ -464,12 +512,15 @@ int kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu)
> {
> struct kvm_cpu_context *host_ctxt;
> struct kvm_cpu_context *guest_ctxt;
> + bool pmu_switch_needed;
> u64 exit_code;
>
> host_ctxt = vcpu->arch.host_cpu_context;
> host_ctxt->__hyp_running_vcpu = vcpu;
> guest_ctxt = &vcpu->arch.ctxt;
>
> + pmu_switch_needed = __pmu_switch_to_guest(host_ctxt);
> +
> sysreg_save_host_state_vhe(host_ctxt);
>
> /*
> @@ -511,6 +562,9 @@ int kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu)
>
> __debug_switch_to_host(vcpu);
>
> + if (pmu_switch_needed)
> + __pmu_switch_to_host(host_ctxt);
> +
> return exit_code;
> }
>
> @@ -519,6 +573,7 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu)
> {
> struct kvm_cpu_context *host_ctxt;
> struct kvm_cpu_context *guest_ctxt;
> + bool pmu_switch_needed;
> u64 exit_code;
>
> vcpu = kern_hyp_va(vcpu);
> @@ -527,6 +582,8 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu)
> host_ctxt->__hyp_running_vcpu = vcpu;
> guest_ctxt = &vcpu->arch.ctxt;
>
> + pmu_switch_needed = __pmu_switch_to_guest(host_ctxt);
> +
> __sysreg_save_state_nvhe(host_ctxt);
>
> __activate_vm(kern_hyp_va(vcpu->kvm));
> @@ -573,6 +630,9 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu)
> */
> __debug_switch_to_host(vcpu);
>
> + if (pmu_switch_needed)
> + __pmu_switch_to_host(host_ctxt);
> +
> return exit_code;
> }
>
> --
> 2.7.4
>
Thanks,
Christoffer
