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>

4 files changed, 42 insertions, 1 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index ae5d7830855c..33fef0738a29 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/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;
diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
index b8f1c0176cbc..462efe746d77 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/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
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0fbdced78737..0b3fd809a3c7 100644
--- a/arch/x86/kvm/x86.c
+++ b/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;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index b647c2917391..932d7f2637d6 100644
--- a/include/uapi/linux/kvm.h
+++ b/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