[PATCH v9 15/17] KVM: x86/vmx: Flip Arch LBREn bit on guest state change

Yang Weijiang
2022-02-16T10:27:41Z

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@intel.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 e7969884d90e..92bdb4101a08 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4603,6 +4603,8 @@ 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);
}
}

@@ -7694,6 +7696,7 @@ 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;
}

@@ -7715,6 +7718,7 @@ 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