linux-kernel - [PATCH v11 13/16] KVM: x86/vmx: Clear Arch LBREn bit before inject #DB to guest

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Message-Id: <20220506033305.5135-14-weijiang.yang@intel.com>
Date:   Thu,  5 May 2022 23:33:02 -0400
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     pbonzini@...hat.com, jmattson@...gle.com, seanjc@...gle.com,
        kan.liang@...ux.intel.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 v11 13/16] 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 e6384ef1d115..6d6ee9cf82f5 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1605,6 +1605,27 @@ 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);
@@ -1640,6 +1661,9 @@ 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,
@@ -4645,6 +4669,9 @@ 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