Hi Andrew,
On 04/12/18 14:58, 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.
>
> 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.mur...@arm.com>
> ---
> arch/arm64/kvm/hyp/switch.c | 41 +++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 41 insertions(+)
>
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index d496ef5..5e03921 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -373,6 +373,35 @@ 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)
> +{
> + u32 host = host_ctxt->events_host;
> + u32 guest = host_ctxt->events_guest;
> +
> + if (host == guest)
> + return false;
> +
> + if (host)
> + write_sysreg(host, pmcntenclr_el0);
Nit:
Instead of clearing host counters we could clear non-guest counters:
u32 clear_events = host_ctxt->events_hosts & ~guest;
if (clear_events)
write_sysreg(clear_events, pmcntenclr_el0);
Don't know if it makes a lot of difference.
> +
> + if (guest)
> + write_sysreg(guest, pmcntenset_el0);
> +
> + return (host || guest);
We know this is true. If both (host == 0 && guest == 0) then (host ==
guest) meaning we returned false.
> +}
> +
> +static void __hyp_text __pmu_switch_to_host(struct kvm_cpu_context
> *host_ctxt)
> +{
> + u32 host = host_ctxt->events_host;
> + u32 guest = host_ctxt->events_guest;
> +
> + if (guest)
> + write_sysreg(guest, pmcntenclr_el0);
Nit:
Same as above, we could just clear the counters that are exclusive to
the guest.
Cheers,
--
Julien Thierry
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