kvm: x86: add host poll control msrs

Add an MSRs which allows the guest to disable
host polling (specifically the cpuidle-haltpoll,
when performing polling in the guest, disables
host side polling).
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Documentation/virtual/kvm/msr.txt

@@ -273,3 +273,12 @@ MSR_KVM_EOI_EN: 0x4b564d04
 	guest must both read the least significant bit in the memory area and
 	clear it using a single CPU instruction, such as test and clear, or
 	compare and exchange.
+
+MSR_KVM_POLL_CONTROL: 0x4b564d05
+	Control host-side polling.
+
+	data: Bit 0 enables (1) or disables (0) host-side HLT polling logic.
+
+	KVM guests can request the host not to poll on HLT, for example if
+	they are performing polling themselves.
+

arch/x86/include/asm/kvm_host.h

@@ -755,6 +755,8 @@ struct kvm_vcpu_arch {
 		struct gfn_to_hva_cache data;
 	} pv_eoi;
 
+	u64 msr_kvm_poll_control;
+
 	/*
 	 * Indicate whether the access faults on its page table in guest
 	 * which is set when fix page fault and used to detect unhandeable

arch/x86/include/uapi/asm/kvm_para.h

@@ -29,6 +29,7 @@
 #define KVM_FEATURE_PV_TLB_FLUSH	9
 #define KVM_FEATURE_ASYNC_PF_VMEXIT	10
 #define KVM_FEATURE_PV_SEND_IPI	11
+#define KVM_FEATURE_POLL_CONTROL	12
 
 #define KVM_HINTS_REALTIME      0
 
@@ -47,6 +48,7 @@
 #define MSR_KVM_ASYNC_PF_EN 0x4b564d02
 #define MSR_KVM_STEAL_TIME  0x4b564d03
 #define MSR_KVM_PV_EOI_EN      0x4b564d04
+#define MSR_KVM_POLL_CONTROL	0x4b564d05
 
 struct kvm_steal_time {
 	__u64 steal;

arch/x86/kvm/Kconfig

@@ -41,6 +41,7 @@ config KVM
 	select PERF_EVENTS
 	select HAVE_KVM_MSI
 	select HAVE_KVM_CPU_RELAX_INTERCEPT
+	select HAVE_KVM_NO_POLL
 	select KVM_GENERIC_DIRTYLOG_READ_PROTECT
 	select KVM_VFIO
 	select SRCU

arch/x86/kvm/cpuid.c

@@ -658,7 +658,8 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 			     (1 << KVM_FEATURE_PV_UNHALT) |
 			     (1 << KVM_FEATURE_PV_TLB_FLUSH) |
 			     (1 << KVM_FEATURE_ASYNC_PF_VMEXIT) |
-			     (1 << KVM_FEATURE_PV_SEND_IPI);
+			     (1 << KVM_FEATURE_PV_SEND_IPI) |
+			     (1 << KVM_FEATURE_POLL_CONTROL);
 
 		if (sched_info_on())
 			entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);

arch/x86/kvm/x86.c

@@ -1177,6 +1177,7 @@ static u32 emulated_msrs[] = {
 	MSR_IA32_POWER_CTL,
 
 	MSR_K7_HWCR,
+	MSR_KVM_POLL_CONTROL,
 };
 
 static unsigned num_emulated_msrs;
@@ -2636,6 +2637,14 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 			return 1;
 		break;
 
+	case MSR_KVM_POLL_CONTROL:
+		/* only enable bit supported */
+		if (data & (-1ULL << 1))
+			return 1;
+
+		vcpu->arch.msr_kvm_poll_control = data;
+		break;
+
 	case MSR_IA32_MCG_CTL:
 	case MSR_IA32_MCG_STATUS:
 	case MSR_IA32_MC0_CTL ... MSR_IA32_MCx_CTL(KVM_MAX_MCE_BANKS) - 1:
@@ -2885,6 +2894,9 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	case MSR_KVM_PV_EOI_EN:
 		msr_info->data = vcpu->arch.pv_eoi.msr_val;
 		break;
+	case MSR_KVM_POLL_CONTROL:
+		msr_info->data = vcpu->arch.msr_kvm_poll_control;
+		break;
 	case MSR_IA32_P5_MC_ADDR:
 	case MSR_IA32_P5_MC_TYPE:
 	case MSR_IA32_MCG_CAP:
@@ -8861,6 +8873,10 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
 	msr.host_initiated = true;
 	kvm_write_tsc(vcpu, &msr);
 	vcpu_put(vcpu);
+
+	/* poll control enabled by default */
+	vcpu->arch.msr_kvm_poll_control = 1;
+
 	mutex_unlock(&vcpu->mutex);
 
 	if (!kvmclock_periodic_sync)
@@ -9972,6 +9988,13 @@ bool kvm_vector_hashing_enabled(void)
 }
 EXPORT_SYMBOL_GPL(kvm_vector_hashing_enabled);
 
+bool kvm_arch_no_poll(struct kvm_vcpu *vcpu)
+{
+	return (vcpu->arch.msr_kvm_poll_control & 1) == 0;
+}
+EXPORT_SYMBOL_GPL(kvm_arch_no_poll);
+
+
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_fast_mmio);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_inj_virq);