linux-kernel - [PATCH v11 14/16] KVM: x86/vmx: Flip Arch LBREn bit on guest state change

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Message-Id: <20220506033305.5135-15-weijiang.yang@intel.com>
Date:   Thu,  5 May 2022 23:33:03 -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 14/16] KVM: x86/vmx: Flip Arch LBREn bit on guest state change

Per spec:"IA32_LBR_CTL.LBREn is saved and cleared on #SMI, and restored
on RSM. On a warm reset, all LBR MSRs, including IA32_LBR_DEPTH, have their
values preserved. However, IA32_LBR_CTL.LBREn is cleared to 0, disabling
LBRs." So clear Arch LBREn bit on #SMI and restore it on RSM manully, also
clear the bit when guest does warm reset.

Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
---
 arch/x86/kvm/vmx/vmx.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 6d6ee9cf82f5..b38f58868905 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4593,6 +4593,8 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 	if (!init_event) {
 		if (static_cpu_has(X86_FEATURE_ARCH_LBR))
 			vmcs_write64(GUEST_IA32_LBR_CTL, 0);
+	} else {
+		flip_arch_lbr_ctl(vcpu, false);
 	}
 }
 
@@ -7704,6 +7706,7 @@ static int vmx_enter_smm(struct kvm_vcpu *vcpu, char *smstate)
 	vmx->nested.smm.vmxon = vmx->nested.vmxon;
 	vmx->nested.vmxon = false;
 	vmx_clear_hlt(vcpu);
+	flip_arch_lbr_ctl(vcpu, false);
 	return 0;
 }
 
@@ -7725,6 +7728,7 @@ static int vmx_leave_smm(struct kvm_vcpu *vcpu, const char *smstate)
 		vmx->nested.nested_run_pending = 1;
 		vmx->nested.smm.guest_mode = false;
 	}
+	flip_arch_lbr_ctl(vcpu, true);
 	return 0;
 }
 
-- 
2.27.0