kvm-vmx: add module parameter to avoid trapping HLT instructions (v5)

Commit Message

Anthony Liguori Dec. 6, 2010, 4:53 p.m. UTC

None

Patch

diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 42d9590..9642c22 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 caa967e..e9dbecf 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 +1012,18 @@  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 +1050,7 @@  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 +1435,7 @@  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 +1448,10 @@  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 +2748,7 @@  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 +2841,7 @@  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 +2869,7 @@  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)