[PATCH RFC v2 13/17] KVM: x86/pmu: Add hook to emulate pebs for cross-mapped counters

[Like Xu <like.xu@xxxxxxxxxxxxxxx>]

To emulate PEBS facility, KVM may needs setup context such as
guest DS PEBS fields correctly before vm-entry and this part
will be implemented in the vmx handle_event() hook.

When the cross-map happens to any enabled PEBS counter, it will make
PMU request and exit to kvm_pmu_handle_event() for some rewrite stuff
and then back to cross-map check again and finally to vm-entry.

In this hook, KVM would rewrite the state for the guest and it won't
move events, hence races with the NMI PMI are not a problem.

Signed-off-by: Like Xu <like.xu@xxxxxxxxxxxxxxx>
---
 arch/x86/kvm/pmu.c           | 3 +++
 arch/x86/kvm/pmu.h           | 1 +
 arch/x86/kvm/vmx/pmu_intel.c | 9 +++++++++
 arch/x86/kvm/vmx/vmx.c       | 3 ---
 4 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index a6c5951a5728..f87be3c2140e 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -339,6 +339,9 @@ void kvm_pmu_handle_event(struct kvm_vcpu *vcpu)
 	 */
 	if (unlikely(pmu->need_cleanup))
 		kvm_pmu_cleanup(vcpu);
+
+	if (kvm_x86_ops.pmu_ops->handle_event)
+		kvm_x86_ops.pmu_ops->handle_event(vcpu);
 }
 
 /* check if idx is a valid index to access PMU */
diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
index f5ec94e9a1dc..b1e52e33f08c 100644
--- a/arch/x86/kvm/pmu.h
+++ b/arch/x86/kvm/pmu.h
@@ -45,6 +45,7 @@ struct kvm_pmu_ops {
 	void (*refresh)(struct kvm_vcpu *vcpu);
 	void (*init)(struct kvm_vcpu *vcpu);
 	void (*reset)(struct kvm_vcpu *vcpu);
+	void (*handle_event)(struct kvm_vcpu *vcpu);
 };
 
 static inline u64 pmc_bitmask(struct kvm_pmc *pmc)
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 99d9453e0176..2917105e584e 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -491,6 +491,14 @@ static void intel_pmu_reset(struct kvm_vcpu *vcpu)
 		pmu->global_ovf_ctrl = 0;
 }
 
+void intel_pmu_handle_event(struct kvm_vcpu *vcpu)
+{
+	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
+
+	if (!(pmu->global_ctrl & pmu->pebs_enable))
+		return;
+}
+
 struct kvm_pmu_ops intel_pmu_ops = {
 	.find_arch_event = intel_find_arch_event,
 	.find_fixed_event = intel_find_fixed_event,
@@ -505,4 +513,5 @@ struct kvm_pmu_ops intel_pmu_ops = {
 	.refresh = intel_pmu_refresh,
 	.init = intel_pmu_init,
 	.reset = intel_pmu_reset,
+	.handle_event = intel_pmu_handle_event,
 };
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 302808ec9699..3b62907c8959 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6556,9 +6556,6 @@ static void atomic_switch_perf_msrs(struct vcpu_vmx *vmx)
 	if (!msrs)
 		return;
 
-	if (pmu->counter_cross_mapped)
-		msrs[1].guest = 0;
-
 	if (nr_msrs > 2 && msrs[1].guest) {
 		msrs[2].guest = pmu->ds_area;
 		if (nr_msrs > 3)
-- 
2.21.3