3 files changed, 19 insertions, 10 deletions

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 4df9af4f6132..e2a4b5287361 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1100,6 +1100,15 @@ emulate them efficiently. The fields in each entry are defined as follows:
    eax, ebx, ecx, edx: the values returned by the cpuid instruction for
          this function/index combination
 
+The TSC deadline timer feature (CPUID leaf 1, ecx[24]) is always returned
+as false, since the feature depends on KVM_CREATE_IRQCHIP for local APIC
+support.  Instead it is reported via
+
+  ioctl(KVM_CHECK_EXTENSION, KVM_CAP_TSC_DEADLINE_TIMER)
+
+if that returns true and you use KVM_CREATE_IRQCHIP, or if you emulate the
+feature in userspace, then you can enable the feature for KVM_SET_CPUID2.
+
 4.47 KVM_PPC_GET_PVINFO
 
 Capability: KVM_CAP_PPC_GET_PVINFO
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c38efd7b792e..4c938da2ba00 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -602,7 +602,6 @@ static void update_cpuid(struct kvm_vcpu *vcpu)
 {
         struct kvm_cpuid_entry2 *best;
         struct kvm_lapic *apic = vcpu->arch.apic;
-        u32 timer_mode_mask;
 
         best = kvm_find_cpuid_entry(vcpu, 1, 0);
         if (!best)
@@ -615,15 +614,12 @@ static void update_cpuid(struct kvm_vcpu *vcpu)
                         best->ecx |= bit(X86_FEATURE_OSXSAVE);
         }
 
-        if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
-                best->function == 0x1) {
-                best->ecx |= bit(X86_FEATURE_TSC_DEADLINE_TIMER);
-                timer_mode_mask = 3 << 17;
-        } else
-                timer_mode_mask = 1 << 17;
-
-        if (apic)
-                apic->lapic_timer.timer_mode_mask = timer_mode_mask;
+        if (apic) {
+                if (best->ecx & bit(X86_FEATURE_TSC_DEADLINE_TIMER))
+                        apic->lapic_timer.timer_mode_mask = 3 << 17;
+                else
+                        apic->lapic_timer.timer_mode_mask = 1 << 17;
+        }
 }
 
 int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
@@ -2135,6 +2131,9 @@ int kvm_dev_ioctl_check_extension(long ext)
         case KVM_CAP_TSC_CONTROL:
                 r = kvm_has_tsc_control;
                 break;
+        case KVM_CAP_TSC_DEADLINE_TIMER:
+                r = boot_cpu_has(X86_FEATURE_TSC_DEADLINE_TIMER);
+                break;
         default:
                 r = 0;
                 break;
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index c3892fc1d538..68e67e50d028 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -557,6 +557,7 @@ struct kvm_ppc_pvinfo {
 #define KVM_CAP_MAX_VCPUS 66       /* returns max vcpus per vm */
 #define KVM_CAP_PPC_PAPR 68
 #define KVM_CAP_S390_GMAP 71
+#define KVM_CAP_TSC_DEADLINE_TIMER 72
 
 #ifdef KVM_CAP_IRQ_ROUTING