arm64: KVM: Enable VHE support for :G/:H perf event modifiers

With VHE different exception levels are used between the host (EL2) and
guest (EL1) with a shared exception level for userpace (EL0). We can take
advantage of this and use the PMU's exception level filtering to avoid
enabling/disabling counters in the world-switch code. Instead we just
modify the counter type to include or exclude EL0 at vcpu_{load,put} time.

We also ensure that trapped PMU system register writes do not re-enable
EL0 when reconfiguring the backing perf events.

This approach completely avoids blackout windows seen with !VHE.

Suggested-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Andrew Murray <andrew.murray@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index e960b91551d6..8b7ca101f0f7 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -382,6 +382,7 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
         kvm_timer_vcpu_load(vcpu);
         kvm_vcpu_load_sysregs(vcpu);
         kvm_arch_vcpu_load_fp(vcpu);
+        kvm_vcpu_pmu_restore_guest(vcpu);
 
         if (single_task_running())
                 vcpu_clear_wfe_traps(vcpu);
@@ -397,6 +398,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
         kvm_vcpu_put_sysregs(vcpu);
         kvm_timer_vcpu_put(vcpu);
         kvm_vgic_put(vcpu);
+        kvm_vcpu_pmu_restore_host(vcpu);
 
         vcpu->cpu = -1;