2 files changed, 29 insertions, 2 deletions

diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 42d959056f97..9642c2216f31 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -297,6 +297,12 @@ enum vmcs_field {
 #define GUEST_INTR_STATE_SMI            0x00000004
 #define GUEST_INTR_STATE_NMI            0x00000008
 
+/* GUEST_ACTIVITY_STATE flags */
+#define GUEST_ACTIVITY_ACTIVE           0
+#define GUEST_ACTIVITY_HLT              1
+#define GUEST_ACTIVITY_SHUTDOWN         2
+#define GUEST_ACTIVITY_WAIT_SIPI        3
+
 /*
  * Exit Qualifications for MOV for Control Register Access
  */
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index f3693ca93982..c1952603d580 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -69,6 +69,9 @@ module_param(emulate_invalid_guest_state, bool, S_IRUGO);
 static int __read_mostly vmm_exclusive = 1;
 module_param(vmm_exclusive, bool, S_IRUGO);
 
+static int __read_mostly yield_on_hlt = 1;
+module_param(yield_on_hlt, bool, S_IRUGO);
+
 #define KVM_GUEST_CR0_MASK_UNRESTRICTED_GUEST                           \
         (X86_CR0_WP | X86_CR0_NE | X86_CR0_NW | X86_CR0_CD)
 #define KVM_GUEST_CR0_MASK                                              \
@@ -1009,6 +1012,17 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu)
         vmx_set_interrupt_shadow(vcpu, 0);
 }
 
+static void vmx_clear_hlt(struct kvm_vcpu *vcpu)
+{
+        /* Ensure that we clear the HLT state in the VMCS.  We don't need to
+         * explicitly skip the instruction because if the HLT state is set, then
+         * the instruction is already executing and RIP has already been
+         * advanced. */
+        if (!yield_on_hlt &&
+            vmcs_read32(GUEST_ACTIVITY_STATE) == GUEST_ACTIVITY_HLT)
+                vmcs_write32(GUEST_ACTIVITY_STATE, GUEST_ACTIVITY_ACTIVE);
+}
+
 static void vmx_queue_exception(struct kvm_vcpu *vcpu, unsigned nr,
                                 bool has_error_code, u32 error_code,
                                 bool reinject)
@@ -1035,6 +1049,7 @@ static void vmx_queue_exception(struct kvm_vcpu *vcpu, unsigned nr,
                 intr_info |= INTR_TYPE_HARD_EXCEPTION;
 
         vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, intr_info);
+        vmx_clear_hlt(vcpu);
 }
 
 static bool vmx_rdtscp_supported(void)
@@ -1419,7 +1434,7 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf)
                                 &_pin_based_exec_control) < 0)
                 return -EIO;
 
-        min = CPU_BASED_HLT_EXITING |
+        min =
 #ifdef CONFIG_X86_64
               CPU_BASED_CR8_LOAD_EXITING |
               CPU_BASED_CR8_STORE_EXITING |
@@ -1432,6 +1447,10 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf)
               CPU_BASED_MWAIT_EXITING |
               CPU_BASED_MONITOR_EXITING |
               CPU_BASED_INVLPG_EXITING;
+
+        if (yield_on_hlt)
+                min |= CPU_BASED_HLT_EXITING;
+
         opt = CPU_BASED_TPR_SHADOW |
               CPU_BASED_USE_MSR_BITMAPS |
               CPU_BASED_ACTIVATE_SECONDARY_CONTROLS;
@@ -2728,7 +2747,7 @@ static int vmx_vcpu_reset(struct kvm_vcpu *vcpu)
         vmcs_writel(GUEST_IDTR_BASE, 0);
         vmcs_write32(GUEST_IDTR_LIMIT, 0xffff);
 
-        vmcs_write32(GUEST_ACTIVITY_STATE, 0);
+        vmcs_write32(GUEST_ACTIVITY_STATE, GUEST_ACTIVITY_ACTIVE);
         vmcs_write32(GUEST_INTERRUPTIBILITY_INFO, 0);
         vmcs_write32(GUEST_PENDING_DBG_EXCEPTIONS, 0);
 
@@ -2821,6 +2840,7 @@ static void vmx_inject_irq(struct kvm_vcpu *vcpu)
         } else
                 intr |= INTR_TYPE_EXT_INTR;
         vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, intr);
+        vmx_clear_hlt(vcpu);
 }
 
 static void vmx_inject_nmi(struct kvm_vcpu *vcpu)
@@ -2848,6 +2868,7 @@ static void vmx_inject_nmi(struct kvm_vcpu *vcpu)
         }
         vmcs_write32(VM_ENTRY_INTR_INFO_FIELD,
                         INTR_TYPE_NMI_INTR | INTR_INFO_VALID_MASK | NMI_VECTOR);
+        vmx_clear_hlt(vcpu);
 }
 
 static int vmx_nmi_allowed(struct kvm_vcpu *vcpu)