[PATCH 23/30] KVM: x86: nSVM: implement nested LBR virtualization

[Maxim Levitsky]

This was tested with kvm-unit-test that was developed
for this purpose.

Signed-off-by: Maxim Levitsky <mlevi...@redhat.com>
---
 arch/x86/kvm/svm/nested.c | 21 +++++++++++++++++++--
 arch/x86/kvm/svm/svm.c    |  8 ++++++++
 arch/x86/kvm/svm/svm.h    |  1 +
 3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 9f7bc7db08dd3..4a228a76b27d7 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -536,8 +536,19 @@ static void nested_vmcb02_prepare_save(struct vcpu_svm 
*svm, struct vmcb *vmcb12
                vmcb_mark_dirty(svm->vmcb, VMCB_DR);
        }
 
-       if (unlikely(svm->vmcb01.ptr->control.virt_ext & LBR_CTL_ENABLE_MASK))
+       if (unlikely(svm->lbrv_enabled && (svm->nested.ctl.virt_ext & 
LBR_CTL_ENABLE_MASK))) {
+
+               /* Copy LBR related registers from vmcb12,
+                * but make sure that we only pick LBR enable bit from the 
guest.
+                */
+
+               svm_copy_lbrs(vmcb12, svm->vmcb);
+               svm->vmcb->save.dbgctl &= LBR_CTL_ENABLE_MASK;
+               svm_update_lbrv(&svm->vcpu);
+
+       } else if (unlikely(svm->vmcb01.ptr->control.virt_ext & 
LBR_CTL_ENABLE_MASK)) {
                svm_copy_lbrs(svm->vmcb01.ptr, svm->vmcb);
+       }
 }
 
 static void nested_vmcb02_prepare_control(struct vcpu_svm *svm)
@@ -592,6 +603,9 @@ static void nested_vmcb02_prepare_control(struct vcpu_svm 
*svm)
 
        svm->vmcb->control.virt_ext            = 
svm->vmcb01.ptr->control.virt_ext &
                                                 LBR_CTL_ENABLE_MASK;
+       if (svm->lbrv_enabled)
+               svm->vmcb->control.virt_ext  |=
+                       (svm->nested.ctl.virt_ext & LBR_CTL_ENABLE_MASK);
 
        nested_svm_transition_tlb_flush(vcpu);
 
@@ -858,7 +872,10 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
 
        svm_switch_vmcb(svm, &svm->vmcb01);
 
-       if (unlikely(svm->vmcb->control.virt_ext & LBR_CTL_ENABLE_MASK)) {
+       if (unlikely(svm->lbrv_enabled && (svm->nested.ctl.virt_ext & 
LBR_CTL_ENABLE_MASK))) {
+               svm_copy_lbrs(svm->nested.vmcb02.ptr, vmcb12);
+               svm_update_lbrv(vcpu);
+       } else if (unlikely(svm->vmcb->control.virt_ext & LBR_CTL_ENABLE_MASK)) 
{
                svm_copy_lbrs(svm->nested.vmcb02.ptr, svm->vmcb);
                svm_update_lbrv(vcpu);
        }
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 294e016f575a8..76aa6054d9db2 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -890,6 +890,10 @@ void svm_update_lbrv(struct kvm_vcpu *vcpu)
        bool current_enable_lbrv = !!(svm->vmcb->control.virt_ext &
                                      LBR_CTL_ENABLE_MASK);
 
+       if (unlikely(is_guest_mode(vcpu) && svm->lbrv_enabled))
+               if (unlikely(svm->nested.ctl.virt_ext & LBR_CTL_ENABLE_MASK))
+                       enable_lbrv = true;
+
        if (enable_lbrv == current_enable_lbrv)
                return;
 
@@ -3987,6 +3991,7 @@ static void svm_vcpu_after_set_cpuid(struct kvm_vcpu 
*vcpu)
                             guest_cpuid_has(vcpu, X86_FEATURE_NRIPS);
 
        svm->tsc_scaling_enabled = tsc_scaling && guest_cpuid_has(vcpu, 
X86_FEATURE_TSCRATEMSR);
+       svm->lbrv_enabled = lbrv && guest_cpuid_has(vcpu, X86_FEATURE_LBRV);
 
        svm_recalc_instruction_intercepts(vcpu, svm);
 
@@ -4791,6 +4796,9 @@ static __init void svm_set_cpu_caps(void)
                if (tsc_scaling)
                        kvm_cpu_cap_set(X86_FEATURE_TSCRATEMSR);
 
+               if (lbrv)
+                       kvm_cpu_cap_set(X86_FEATURE_LBRV);
+
                /* Nested VM can receive #VMEXIT instead of triggering #GP */
                kvm_cpu_cap_set(X86_FEATURE_SVME_ADDR_CHK);
        }
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index b83e06d5d942a..0012ba5affcba 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -220,6 +220,7 @@ struct vcpu_svm {
        /* cached guest cpuid flags for faster access */
        bool nrips_enabled                : 1;
        bool tsc_scaling_enabled          : 1;
+       bool lbrv_enabled                 : 1;
 
        u32 ldr_reg;
        u32 dfr_reg;
-- 
2.26.3