[PATCH v2 3/8] KVM/vmx: Pass through the lbr stack to a guest

[Wei Wang]

Pass through the LBR stack to the guest when the guest lbr feature is
enabled. This makes the guest have direct accesses to the lbr stack.

Signed-off-by: Like Xu <like.xu@xxxxxxxxx>
Signed-off-by: Wei Wang <wei.w.wang@xxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
---
 arch/x86/kvm/vmx.c | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 1d26f3c..7a62c1c 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -7847,6 +7847,38 @@ static void vmx_enable_tdp(void)
 	kvm_enable_tdp();
 }
 
+static int vmx_passthrough_lbr_msrs(struct kvm *kvm,
+				     unsigned long *msr_bitmap)
+{
+	int i;
+	struct perf_lbr_stack lbr_stack;
+
+	if (perf_get_lbr_stack(&lbr_stack) < 0) {
+		pr_err("Failed to pass through the lbr stack\n");
+		return -ENOENT;
+	}
+
+	vmx_disable_intercept_for_msr(msr_bitmap, MSR_LBR_SELECT,
+				      MSR_TYPE_RW);
+	vmx_disable_intercept_for_msr(msr_bitmap, lbr_stack.lbr_tos,
+				      MSR_TYPE_RW);
+
+	for (i = 0; i < lbr_stack.lbr_nr; i++) {
+		vmx_disable_intercept_for_msr(msr_bitmap,
+					      lbr_stack.lbr_from + i,
+					      MSR_TYPE_RW);
+		vmx_disable_intercept_for_msr(msr_bitmap,
+					      lbr_stack.lbr_to + i,
+					      MSR_TYPE_RW);
+		if (lbr_stack.lbr_info)
+			vmx_disable_intercept_for_msr(msr_bitmap,
+						      lbr_stack.lbr_info + i,
+						      MSR_TYPE_RW);
+	}
+
+	return 0;
+}
+
 static __init int hardware_setup(void)
 {
 	unsigned long host_bndcfgs;
@@ -10998,6 +11030,12 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
 	vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_SYSENTER_EIP, MSR_TYPE_RW);
 	vmx->msr_bitmap_mode = 0;
 
+	if (kvm->arch.guest_lbr) {
+		err = vmx_passthrough_lbr_msrs(kvm, msr_bitmap);
+		if (err < 0)
+			goto free_vmcs;
+	}
+
 	vmx->loaded_vmcs = &vmx->vmcs01;
 	cpu = get_cpu();
 	vmx_vcpu_load(&vmx->vcpu, cpu);
-- 
2.7.4