add support for Hyper-V reference time counter

Signed-off: Peter Lieven <pl@kamp.de>
Signed-off: Gleb Natapov
Signed-off: Vadim Rozenfeld <vrozenfe@redhat.com>

After some consideration I decided to submit only Hyper-V reference
counters support this time. I will submit iTSC support as a separate
patch as soon as it is ready.

v1 -> v2
1. mark TSC page dirty as suggested by
    Eric Northup <digitaleric@google.com> and Gleb
2. disable local irq when calling get_kernel_ns,
    as it was done by Peter Lieven <pl@amp.de>
3. move check for TSC page enable from second patch
    to this one.

v3 -> v4
    Get rid of ref counter offset.

v4 -> v5
    replace __copy_to_user with kvm_write_guest
    when updateing iTSC page.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -605,6 +605,7 @@ struct kvm_arch {
 	/* fields used by HYPER-V emulation */
 	u64 hv_guest_os_id;
 	u64 hv_hypercall;
+	u64 hv_tsc_page;
 
 	#ifdef CONFIG_KVM_MMU_AUDIT
 	int audit_point;

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

@@ -28,6 +28,9 @@
 /* Partition Reference Counter (HV_X64_MSR_TIME_REF_COUNT) available*/
 #define HV_X64_MSR_TIME_REF_COUNT_AVAILABLE	(1 << 1)
 
+/* A partition's reference time stamp counter (TSC) page */
+#define HV_X64_MSR_REFERENCE_TSC		0x40000021
+
 /*
  * There is a single feature flag that signifies the presence of the MSR
  * that can be used to retrieve both the local APIC Timer frequency as
@@ -198,6 +201,9 @@
 #define HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_MASK	\
 		(~((1ull << HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_SHIFT) - 1))
 
+#define HV_X64_MSR_TSC_REFERENCE_ENABLE		0x00000001
+#define HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT	12
+
 #define HV_PROCESSOR_POWER_STATE_C0		0
 #define HV_PROCESSOR_POWER_STATE_C1		1
 #define HV_PROCESSOR_POWER_STATE_C2		2
@@ -210,4 +216,11 @@
 #define HV_STATUS_INVALID_ALIGNMENT		4
 #define HV_STATUS_INSUFFICIENT_BUFFERS		19
 
+typedef struct _HV_REFERENCE_TSC_PAGE {
+	__u32 tsc_sequence;
+	__u32 res1;
+	__u64 tsc_scale;
+	__s64 tsc_offset;
+} HV_REFERENCE_TSC_PAGE, *PHV_REFERENCE_TSC_PAGE;
+
 #endif

arch/x86/kvm/x86.c

@@ -839,11 +839,12 @@ EXPORT_SYMBOL_GPL(kvm_rdpmc);
  * kvm-specific. Those are put in the beginning of the list.
  */
 
-#define KVM_SAVE_MSRS_BEGIN	10
+#define KVM_SAVE_MSRS_BEGIN	12
 static u32 msrs_to_save[] = {
 	MSR_KVM_SYSTEM_TIME, MSR_KVM_WALL_CLOCK,
 	MSR_KVM_SYSTEM_TIME_NEW, MSR_KVM_WALL_CLOCK_NEW,
 	HV_X64_MSR_GUEST_OS_ID, HV_X64_MSR_HYPERCALL,
+	HV_X64_MSR_TIME_REF_COUNT, HV_X64_MSR_REFERENCE_TSC,
 	HV_X64_MSR_APIC_ASSIST_PAGE, MSR_KVM_ASYNC_PF_EN, MSR_KVM_STEAL_TIME,
 	MSR_KVM_PV_EOI_EN,
 	MSR_IA32_SYSENTER_CS, MSR_IA32_SYSENTER_ESP, MSR_IA32_SYSENTER_EIP,
@@ -1788,6 +1789,8 @@ static bool kvm_hv_msr_partition_wide(u32 msr)
 	switch (msr) {
 	case HV_X64_MSR_GUEST_OS_ID:
 	case HV_X64_MSR_HYPERCALL:
+	case HV_X64_MSR_REFERENCE_TSC:
+	case HV_X64_MSR_TIME_REF_COUNT:
 		r = true;
 		break;
 	}
@@ -1829,6 +1832,20 @@ static int set_msr_hyperv_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 		kvm->arch.hv_hypercall = data;
 		break;
 	}
+	case HV_X64_MSR_REFERENCE_TSC: {
+		u64 gfn;
+		HV_REFERENCE_TSC_PAGE tsc_ref;
+		memset(&tsc_ref, 0, sizeof(tsc_ref));
+		kvm->arch.hv_tsc_page = data;
+		if (!(data & HV_X64_MSR_TSC_REFERENCE_ENABLE))
+			break;
+		gfn = data >> HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT;
+		if (kvm_write_guest(kvm, data,
+			&tsc_ref, sizeof(tsc_ref)))
+			return 1;
+		mark_page_dirty(kvm, gfn);
+		break;
+	}
 	default:
 		vcpu_unimpl(vcpu, "HYPER-V unimplemented wrmsr: 0x%x "
 			    "data 0x%llx\n", msr, data);
@@ -2253,6 +2270,14 @@ static int get_msr_hyperv_pw(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
 	case HV_X64_MSR_HYPERCALL:
 		data = kvm->arch.hv_hypercall;
 		break;
+	case HV_X64_MSR_TIME_REF_COUNT: {
+		data =
+		     div_u64(get_kernel_ns() + kvm->arch.kvmclock_offset, 100);
+		break;
+	}
+	case HV_X64_MSR_REFERENCE_TSC:
+		data = kvm->arch.hv_tsc_page;
+		break;
 	default:
 		vcpu_unimpl(vcpu, "Hyper-V unhandled rdmsr: 0x%x\n", msr);
 		return 1;
@@ -2566,6 +2591,7 @@ int kvm_dev_ioctl_check_extension(long ext)
 #ifdef CONFIG_KVM_DEVICE_ASSIGNMENT
 	case KVM_CAP_ASSIGN_DEV_IRQ:
 	case KVM_CAP_PCI_2_3:
+	case KVM_CAP_HYPERV_TIME:
 #endif
 		r = 1;
 		break;

include/uapi/linux/kvm.h

@@ -674,6 +674,7 @@ struct kvm_ppc_smmu_info {
 #define KVM_CAP_ARM_EL1_32BIT 93
 #define KVM_CAP_SPAPR_MULTITCE 94
 #define KVM_CAP_EXT_EMUL_CPUID 95
+#define KVM_CAP_HYPERV_TIME 96
 
 #ifdef KVM_CAP_IRQ_ROUTING