[PATCH] KVM: X86: Disable KVM_FEATURE_STEAL_TIME when both delayacct_on added to cmdline and CONFIG_SCHEDSTATS is set

[Chen Xiao]

From: Chen Xiao <abigwc@xxxxxxx>

When sched_info_on returns 1ïKVM_FEATURE_STEAL_TIME will be set,
steal% can be seen in the virtual machine.The returned value of
sched_info_on depends on delayacct_on. If nodelayacct is added to
kernel boot cmdline,the KVM_FEATURE_STEAL_TIME will be turned off
by setting delayacct_on to 0.When CONFIG_SCHEDSTATS is set, sched_info_on
always returns 1, and adding nodelayacct to the cmdline cannot turn
off the KVM_FEATURE_STEAL_TIME Sometimes the users do not want the
running state of host to be perceived in the virtual machine, and 
intend to turn off KVM_FEATURE_STEAL_TIME. The requirement is not
available, however, when CONFIG_SCHEDSTATS has been set.Modify the
judgment criteria for being set up from KVM_FEATURE_STEAL_TIME, and
it is only be judged by the value of delayacct_on.

Signed-off-by: Chen Xiao <abigwc@xxxxxxxxx>
---
 arch/x86/kvm/cpuid.c |  2 +-
 arch/x86/kvm/x86.c   |  8 ++++----
 arch/x86/kvm/x86.h   | 10 ++++++++++
 3 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 7e042e3..d38da09 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -623,7 +623,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 			     (1 << KVM_FEATURE_PV_TLB_FLUSH) |
 			     (1 << KVM_FEATURE_ASYNC_PF_VMEXIT);
 
-		if (sched_info_on())
+		if (kvm_feature_steal_on())
 			entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);
 
 		entry->ebx = 0;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2b812b3..8371d5c 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2424,8 +2424,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 			return 1;
 		break;
 	case MSR_KVM_STEAL_TIME:
-
-		if (unlikely(!sched_info_on()))
+		if (unlikely(!kvm_feature_steal_on()))
 			return 1;
 
 		if (data & KVM_STEAL_RESERVED_MASK)
@@ -3101,7 +3100,8 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 		vcpu->cpu = cpu;
 	}
 
-	kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
+	if (kvm_feature_steal_on())
+		kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
 }
 
 static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
@@ -7291,7 +7291,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 			r = 1;
 			goto out;
 		}
-		if (kvm_check_request(KVM_REQ_STEAL_UPDATE, vcpu))
+		if (kvm_feature_steal_on()
+		&& kvm_check_request(KVM_REQ_STEAL_UPDATE, vcpu))
 			record_steal_time(vcpu);
 		if (kvm_check_request(KVM_REQ_SMI, vcpu))
 			process_smi(vcpu);
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 257f276..9e7c078 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -338,4 +338,14 @@ static inline void kvm_after_interrupt(struct kvm_vcpu *vcpu)
 	__this_cpu_write(current_vcpu, NULL);
 }
 
+static inline int kvm_feature_steal_on(void)
+{
+#ifdef CONFIG_TASK_DELAY_ACCT
+	extern int delayacct_on;
+	return delayacct_on;
+#else
+	return 0;
+#endif
+}
+
 #endif
-- 
1.8.3.1