linux-kernel - [PATCH v8 14/15] KVM: x86/vmx: Flip Arch LBREn bit on guest state change

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Message-Id: <1629791777-16430-15-git-send-email-weijiang.yang@intel.com>
Date:   Tue, 24 Aug 2021 15:56:16 +0800
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 v8 14/15] 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 | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 316403cb4038..ea1efb48d1d6 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4519,8 +4519,10 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 	vmx_update_exception_bitmap(vcpu);
 
 	vpid_sync_context(vmx->vpid);
-	if (init_event)
+	if (init_event) {
 		vmx_clear_hlt(vcpu);
+		flip_arch_lbr_ctl(vcpu, false);
+	}
 }
 
 static void vmx_enable_irq_window(struct kvm_vcpu *vcpu)
@@ -7523,6 +7525,7 @@ 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;
 }
 
@@ -7543,6 +7546,7 @@ static int vmx_leave_smm(struct kvm_vcpu *vcpu, const char *smstate)
 
 		vmx->nested.smm.guest_mode = false;
 	}
+	flip_arch_lbr_ctl(vcpu, true);
 	return 0;
 }
 
-- 
2.25.1