linux-kernel - [PATCH v9 14/17] KVM: x86/vmx: Clear Arch LBREn bit before inject #DB to guest

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Date:   Tue, 15 Feb 2022 16:25:41 -0500
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     pbonzini@...hat.com, jmattson@...gle.com, seanjc@...gle.com,
        like.xu.linux@...il.com, vkuznets@...hat.com, wei.w.wang@...el.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Yang Weijiang <weijiang.yang@...el.com>
Subject: [PATCH v9 14/17] KVM: x86/vmx: Clear Arch LBREn bit before inject #DB to guest

On a debug breakpoint event (#DB), IA32_LBR_CTL.LBREn is cleared.
So need to clear the bit manually before inject #DB.

Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
---
 arch/x86/kvm/vmx/vmx.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d1eb1e149fea..e7969884d90e 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1617,6 +1617,27 @@ static void vmx_clear_hlt(struct kvm_vcpu *vcpu)
 		vmcs_write32(GUEST_ACTIVITY_STATE, GUEST_ACTIVITY_ACTIVE);
 }
 
+static void flip_arch_lbr_ctl(struct kvm_vcpu *vcpu, bool on)
+{
+	struct lbr_desc *lbr_desc = vcpu_to_lbr_desc(vcpu);
+	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
+
+	if (kvm_cpu_cap_has(X86_FEATURE_ARCH_LBR) &&
+	    test_bit(INTEL_PMC_IDX_FIXED_VLBR, pmu->pmc_in_use) &&
+	    lbr_desc->event) {
+		u64 old = vmcs_read64(GUEST_IA32_LBR_CTL);
+		u64 new;
+
+		if (on)
+			new = old | ARCH_LBR_CTL_LBREN;
+		else
+			new = old & ~ARCH_LBR_CTL_LBREN;
+
+		if (old != new)
+			vmcs_write64(GUEST_IA32_LBR_CTL, new);
+	}
+}
+
 static void vmx_queue_exception(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -1652,6 +1673,9 @@ static void vmx_queue_exception(struct kvm_vcpu *vcpu)
 	vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, intr_info);
 
 	vmx_clear_hlt(vcpu);
+
+	if (nr == DB_VECTOR)
+		flip_arch_lbr_ctl(vcpu, false);
 }
 
 static void vmx_setup_uret_msr(struct vcpu_vmx *vmx, unsigned int msr,
@@ -4655,6 +4679,9 @@ static void vmx_inject_nmi(struct kvm_vcpu *vcpu)
 			INTR_TYPE_NMI_INTR | INTR_INFO_VALID_MASK | NMI_VECTOR);
 
 	vmx_clear_hlt(vcpu);
+
+	if (vcpu->arch.exception.nr == DB_VECTOR)
+		flip_arch_lbr_ctl(vcpu, false);
 }
 
 bool vmx_get_nmi_mask(struct kvm_vcpu *vcpu)
-- 
2.27.0