[RFC PATCH 28/41] KVM: x86/pmu: Switch IA32_PERF_GLOBAL_CTRL at VM boundary

[Xiong Zhang]

From: Xiong Zhang <xiong.y.zhang@xxxxxxxxx>

In PMU passthrough mode, use global_ctrl field in struct kvm_pmu as the
cached value. This is convenient for KVM to set and get the value from the
host side. In addition, load and save the value across VM enter/exit
boundary in the following way:

 - At VM exit, if processor supports
   GUEST_VM_EXIT_SAVE_IA32_PERF_GLOBAL_CTRL, read guest
   IA32_PERF_GLOBAL_CTRL GUEST_IA32_PERF_GLOBAL_CTRL VMCS field, else read
   it from VM-exit MSR-stroe array in VMCS. The value is then assigned to
   global_ctrl.

 - At VM Entry, if processor supports
   GUEST_VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL, read guest
   IA32_PERF_GLOBAL_CTRL from GUEST_IA32_PERF_GLOBAL_CTRL VMCS field, else
   read it from VM-entry MSR-load array in VMCS. The value is then
   assigned to global ctrl.

Implement the above logic into two helper functions and invoke them around
VM Enter/exit boundary.

Co-developed-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
Signed-off-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
Signed-off-by: Xiong Zhang <xiong.y.zhang@xxxxxxxxx>
---
 arch/x86/kvm/vmx/vmx.c | 51 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 50 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 50100954cd92..a9623351eafe 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7193,7 +7193,7 @@ static void vmx_cancel_injection(struct kvm_vcpu *vcpu)
 	vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, 0);
 }
 
-static void atomic_switch_perf_msrs(struct vcpu_vmx *vmx)
+static void __atomic_switch_perf_msrs(struct vcpu_vmx *vmx)
 {
 	int i, nr_msrs;
 	struct perf_guest_switch_msr *msrs;
@@ -7216,6 +7216,52 @@ static void atomic_switch_perf_msrs(struct vcpu_vmx *vmx)
 					msrs[i].host, false);
 }
 
+static void save_perf_global_ctrl_in_passthrough_pmu(struct vcpu_vmx *vmx)
+{
+	struct kvm_pmu *pmu = vcpu_to_pmu(&vmx->vcpu);
+	int i;
+
+	if (vm_exit_controls_get(vmx) & VM_EXIT_SAVE_IA32_PERF_GLOBAL_CTRL) {
+		pmu->global_ctrl = vmcs_read64(GUEST_IA32_PERF_GLOBAL_CTRL);
+	} else {
+		i = vmx_find_loadstore_msr_slot(&vmx->msr_autostore.guest,
+						MSR_CORE_PERF_GLOBAL_CTRL);
+		if (i < 0)
+			return;
+		pmu->global_ctrl = vmx->msr_autostore.guest.val[i].value;
+	}
+}
+
+static void load_perf_global_ctrl_in_passthrough_pmu(struct vcpu_vmx *vmx)
+{
+	u64 global_ctrl = vcpu_to_pmu(&vmx->vcpu)->global_ctrl;
+	int i;
+
+	if (vm_entry_controls_get(vmx) & VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL) {
+		vmcs_write64(GUEST_IA32_PERF_GLOBAL_CTRL, global_ctrl);
+	} else {
+		i = vmx_find_loadstore_msr_slot(&vmx->msr_autoload.guest,
+						MSR_CORE_PERF_GLOBAL_CTRL);
+		if (i < 0)
+			return;
+
+		vmx->msr_autoload.guest.val[i].value = global_ctrl;
+	}
+}
+
+static void __atomic_switch_perf_msrs_in_passthrough_pmu(struct vcpu_vmx *vmx)
+{
+	load_perf_global_ctrl_in_passthrough_pmu(vmx);
+}
+
+static void atomic_switch_perf_msrs(struct vcpu_vmx *vmx)
+{
+	if (is_passthrough_pmu_enabled(&vmx->vcpu))
+		__atomic_switch_perf_msrs_in_passthrough_pmu(vmx);
+	else
+		__atomic_switch_perf_msrs(vmx);
+}
+
 static void vmx_update_hv_timer(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -7314,6 +7360,9 @@ static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
 	vcpu->arch.cr2 = native_read_cr2();
 	vcpu->arch.regs_avail &= ~VMX_REGS_LAZY_LOAD_SET;
 
+	if (is_passthrough_pmu_enabled(vcpu))
+		save_perf_global_ctrl_in_passthrough_pmu(vmx);
+
 	vmx->idt_vectoring_info = 0;
 
 	vmx_enable_fb_clear(vmx);
-- 
2.34.1