check enabled Hyper-V Enlightenment inside VM

check-hyperv-enlightenment.c

#include <intrin.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>

/******************************************************************************/
// include/qemu/bitops.h

#define BIT(nr)                 (1UL << (nr))

/******************************************************************************/
// target/i386/kvm/hyperv-proto.h

#define HV_CPUID_VENDOR_AND_MAX_FUNCTIONS     0x40000000
#define HV_CPUID_INTERFACE                    0x40000001
#define HV_CPUID_VERSION                      0x40000002
#define HV_CPUID_FEATURES                     0x40000003
#define HV_CPUID_ENLIGHTMENT_INFO             0x40000004
#define HV_CPUID_IMPLEMENT_LIMITS             0x40000005
#define HV_CPUID_NESTED_FEATURES              0x4000000A
#define HV_CPUID_SYNDBG_VENDOR_AND_MAX_FUNCTIONS    0x40000080
#define HV_CPUID_SYNDBG_INTERFACE                   0x40000081
#define HV_CPUID_SYNDBG_PLATFORM_CAPABILITIES       0x40000082
#define HV_CPUID_MIN                          0x40000005
#define HV_CPUID_MAX                          0x4000ffff
#define HV_HYPERVISOR_PRESENT_BIT             0x80000000

/*
 * HV_CPUID_FEATURES.EAX bits
 */
#define HV_VP_RUNTIME_AVAILABLE      (1u << 0)
#define HV_TIME_REF_COUNT_AVAILABLE  (1u << 1)
#define HV_SYNIC_AVAILABLE           (1u << 2)
#define HV_SYNTIMERS_AVAILABLE       (1u << 3)
#define HV_APIC_ACCESS_AVAILABLE     (1u << 4)
#define HV_HYPERCALL_AVAILABLE       (1u << 5)
#define HV_VP_INDEX_AVAILABLE        (1u << 6)
#define HV_RESET_AVAILABLE           (1u << 7)
#define HV_REFERENCE_TSC_AVAILABLE   (1u << 9)
#define HV_ACCESS_FREQUENCY_MSRS     (1u << 11)
#define HV_ACCESS_REENLIGHTENMENTS_CONTROL  (1u << 13)

 /*
  * HV_CPUID_FEATURES.EBX bits
  */
#define HV_POST_MESSAGES             (1u << 4)
#define HV_SIGNAL_EVENTS             (1u << 5)

  /*
   * HV_CPUID_FEATURES.EDX bits
   */
#define HV_MWAIT_AVAILABLE                      (1u << 0)
#define HV_GUEST_DEBUGGING_AVAILABLE            (1u << 1)
#define HV_PERF_MONITOR_AVAILABLE               (1u << 2)
#define HV_CPU_DYNAMIC_PARTITIONING_AVAILABLE   (1u << 3)
#define HV_HYPERCALL_XMM_INPUT_AVAILABLE        (1u << 4)
#define HV_GUEST_IDLE_STATE_AVAILABLE           (1u << 5)
#define HV_FREQUENCY_MSRS_AVAILABLE             (1u << 8)
#define HV_GUEST_CRASH_MSR_AVAILABLE            (1u << 10)
#define HV_FEATURE_DEBUG_MSRS_AVAILABLE         (1u << 11)
#define HV_EXT_GVA_RANGES_FLUSH_AVAILABLE       (1u << 14)
#define HV_STIMER_DIRECT_MODE_AVAILABLE         (1u << 19)

   /*
    * HV_CPUID_FEATURES.EBX bits
    */
#define HV_PARTITION_DEBUGGING_ALLOWED          (1u << 12)

    /*
     * HV_CPUID_ENLIGHTMENT_INFO.EAX bits
     */
#define HV_AS_SWITCH_RECOMMENDED            (1u << 0)
#define HV_LOCAL_TLB_FLUSH_RECOMMENDED      (1u << 1)
#define HV_REMOTE_TLB_FLUSH_RECOMMENDED     (1u << 2)
#define HV_APIC_ACCESS_RECOMMENDED          (1u << 3)
#define HV_SYSTEM_RESET_RECOMMENDED         (1u << 4)
#define HV_RELAXED_TIMING_RECOMMENDED       (1u << 5)
#define HV_DEPRECATING_AEOI_RECOMMENDED     (1u << 9)
#define HV_CLUSTER_IPI_RECOMMENDED          (1u << 10)
#define HV_EX_PROCESSOR_MASKS_RECOMMENDED   (1u << 11)
#define HV_ENLIGHTENED_VMCS_RECOMMENDED     (1u << 14)
#define HV_NO_NONARCH_CORESHARING           (1u << 18)

     /*
      * HV_CPUID_SYNDBG_PLATFORM_CAPABILITIES.EAX bits
      */
#define HV_SYNDBG_CAP_ALLOW_KERNEL_DEBUGGING    (1u << 1)

      /*
       * HV_CPUID_NESTED_FEATURES.EAX bits
       */
#define HV_NESTED_DIRECT_FLUSH              (1u << 17)
#define HV_NESTED_MSR_BITMAP                (1u << 19)

       /******************************************************************************/
       // target/i386/cpu.h

       /* Supported Hyper-V Enlightenments */
#define HYPERV_FEAT_RELAXED             0
#define HYPERV_FEAT_VAPIC               1
#define HYPERV_FEAT_TIME                2
#define HYPERV_FEAT_CRASH               3
#define HYPERV_FEAT_RESET               4
#define HYPERV_FEAT_VPINDEX             5
#define HYPERV_FEAT_RUNTIME             6
#define HYPERV_FEAT_SYNIC               7
#define HYPERV_FEAT_STIMER              8
#define HYPERV_FEAT_FREQUENCIES         9
#define HYPERV_FEAT_REENLIGHTENMENT     10
#define HYPERV_FEAT_TLBFLUSH            11
#define HYPERV_FEAT_EVMCS               12
#define HYPERV_FEAT_IPI                 13
#define HYPERV_FEAT_STIMER_DIRECT       14
#define HYPERV_FEAT_AVIC                15
#define HYPERV_FEAT_SYNDBG              16
#define HYPERV_FEAT_MSR_BITMAP          17
#define HYPERV_FEAT_XMM_INPUT           18
#define HYPERV_FEAT_TLBFLUSH_EXT        19
#define HYPERV_FEAT_TLBFLUSH_DIRECT     20

/******************************************************************************/
// modified

enum {
    R_EAX = 0,
    R_EBX = 1,
    R_ECX = 2,
    R_EDX = 3,
};

/******************************************************************************/
// target/i386/kvm/kvm.c

static struct {
    const char* desc;
    struct {
        uint32_t func;
        int reg;
        uint32_t bits;
    } flags[2];
    uint64_t dependencies;
    bool skip_passthrough;
} kvm_hyperv_properties[] = {
    [HYPERV_FEAT_RELAXED] = {
        .desc = "relaxed timing (hv-relaxed)",
        .flags = {
            {.func = HV_CPUID_ENLIGHTMENT_INFO, .reg = R_EAX,
             .bits = HV_RELAXED_TIMING_RECOMMENDED}
        }
    },
    [HYPERV_FEAT_VAPIC] = {
        .desc = "virtual APIC (hv-vapic)",
        .flags = {
            {.func = HV_CPUID_FEATURES, .reg = R_EAX,
             .bits = HV_APIC_ACCESS_AVAILABLE}
        }
    },
    [HYPERV_FEAT_TIME] = {
        .desc = "clocksources (hv-time)",
        .flags = {
            {.func = HV_CPUID_FEATURES, .reg = R_EAX,
             .bits = HV_TIME_REF_COUNT_AVAILABLE | HV_REFERENCE_TSC_AVAILABLE}
        }
    },
    [HYPERV_FEAT_CRASH] = {
        .desc = "crash MSRs (hv-crash)",
        .flags = {
            {.func = HV_CPUID_FEATURES, .reg = R_EDX,
             .bits = HV_GUEST_CRASH_MSR_AVAILABLE}
        }
    },
    [HYPERV_FEAT_RESET] = {
        .desc = "reset MSR (hv-reset)",
        .flags = {
            {.func = HV_CPUID_FEATURES, .reg = R_EAX,
             .bits = HV_RESET_AVAILABLE}
        }
    },
    [HYPERV_FEAT_VPINDEX] = {
        .desc = "VP_INDEX MSR (hv-vpindex)",
        .flags = {
            {.func = HV_CPUID_FEATURES, .reg = R_EAX,
             .bits = HV_VP_INDEX_AVAILABLE}
        }
    },
    [HYPERV_FEAT_RUNTIME] = {
        .desc = "VP_RUNTIME MSR (hv-runtime)",
        .flags = {
            {.func = HV_CPUID_FEATURES, .reg = R_EAX,
             .bits = HV_VP_RUNTIME_AVAILABLE}
        }
    },
    [HYPERV_FEAT_SYNIC] = {
        .desc = "synthetic interrupt controller (hv-synic)",
        .flags = {
            {.func = HV_CPUID_FEATURES, .reg = R_EAX,
             .bits = HV_SYNIC_AVAILABLE}
        }
    },
    [HYPERV_FEAT_STIMER] = {
        .desc = "synthetic timers (hv-stimer)",
        .flags = {
            {.func = HV_CPUID_FEATURES, .reg = R_EAX,
             .bits = HV_SYNTIMERS_AVAILABLE}
        },
        .dependencies = BIT(HYPERV_FEAT_SYNIC) | BIT(HYPERV_FEAT_TIME)
    },
    [HYPERV_FEAT_FREQUENCIES] = {
        .desc = "frequency MSRs (hv-frequencies)",
        .flags = {
            {.func = HV_CPUID_FEATURES, .reg = R_EAX,
             .bits = HV_ACCESS_FREQUENCY_MSRS},
            {.func = HV_CPUID_FEATURES, .reg = R_EDX,
             .bits = HV_FREQUENCY_MSRS_AVAILABLE}
        }
    },
    [HYPERV_FEAT_REENLIGHTENMENT] = {
        .desc = "reenlightenment MSRs (hv-reenlightenment)",
        .flags = {
            {.func = HV_CPUID_FEATURES, .reg = R_EAX,
             .bits = HV_ACCESS_REENLIGHTENMENTS_CONTROL}
        }
    },
    [HYPERV_FEAT_TLBFLUSH] = {
        .desc = "paravirtualized TLB flush (hv-tlbflush)",
        .flags = {
            {.func = HV_CPUID_ENLIGHTMENT_INFO, .reg = R_EAX,
             .bits = HV_REMOTE_TLB_FLUSH_RECOMMENDED |
             HV_EX_PROCESSOR_MASKS_RECOMMENDED}
        },
        .dependencies = BIT(HYPERV_FEAT_VPINDEX)
    },
    [HYPERV_FEAT_EVMCS] = {
        .desc = "enlightened VMCS (hv-evmcs)",
        .flags = {
            {.func = HV_CPUID_ENLIGHTMENT_INFO, .reg = R_EAX,
             .bits = HV_ENLIGHTENED_VMCS_RECOMMENDED}
        },
        .dependencies = BIT(HYPERV_FEAT_VAPIC)
    },
    [HYPERV_FEAT_IPI] = {
        .desc = "paravirtualized IPI (hv-ipi)",
        .flags = {
            {.func = HV_CPUID_ENLIGHTMENT_INFO, .reg = R_EAX,
             .bits = HV_CLUSTER_IPI_RECOMMENDED |
             HV_EX_PROCESSOR_MASKS_RECOMMENDED}
        },
        .dependencies = BIT(HYPERV_FEAT_VPINDEX)
    },
    [HYPERV_FEAT_STIMER_DIRECT] = {
        .desc = "direct mode synthetic timers (hv-stimer-direct)",
        .flags = {
            {.func = HV_CPUID_FEATURES, .reg = R_EDX,
             .bits = HV_STIMER_DIRECT_MODE_AVAILABLE}
        },
        .dependencies = BIT(HYPERV_FEAT_STIMER)
    },
    [HYPERV_FEAT_AVIC] = {
        .desc = "AVIC/APICv support (hv-avic/hv-apicv)",
        .flags = {
            {.func = HV_CPUID_ENLIGHTMENT_INFO, .reg = R_EAX,
             .bits = HV_DEPRECATING_AEOI_RECOMMENDED}
        }
    },
    [HYPERV_FEAT_SYNDBG] = {
        .desc = "Enable synthetic kernel debugger channel (hv-syndbg)",
        .flags = {
            {.func = HV_CPUID_FEATURES, .reg = R_EDX,
             .bits = HV_FEATURE_DEBUG_MSRS_AVAILABLE}
        },
        .dependencies = BIT(HYPERV_FEAT_SYNIC) | BIT(HYPERV_FEAT_RELAXED),
        .skip_passthrough = true,
    },
    [HYPERV_FEAT_MSR_BITMAP] = {
        .desc = "enlightened MSR-Bitmap (hv-emsr-bitmap)",
        .flags = {
            {.func = HV_CPUID_NESTED_FEATURES, .reg = R_EAX,
             .bits = HV_NESTED_MSR_BITMAP}
        }
    },
    [HYPERV_FEAT_XMM_INPUT] = {
        .desc = "XMM fast hypercall input (hv-xmm-input)",
        .flags = {
            {.func = HV_CPUID_FEATURES, .reg = R_EDX,
             .bits = HV_HYPERCALL_XMM_INPUT_AVAILABLE}
        }
    },
    [HYPERV_FEAT_TLBFLUSH_EXT] = {
        .desc = "Extended gva ranges for TLB flush hypercalls (hv-tlbflush-ext)",
        .flags = {
            {.func = HV_CPUID_FEATURES, .reg = R_EDX,
             .bits = HV_EXT_GVA_RANGES_FLUSH_AVAILABLE}
        },
        .dependencies = BIT(HYPERV_FEAT_TLBFLUSH)
    },
    [HYPERV_FEAT_TLBFLUSH_DIRECT] = {
        .desc = "direct TLB flush (hv-tlbflush-direct)",
        .flags = {
            {.func = HV_CPUID_NESTED_FEATURES, .reg = R_EAX,
             .bits = HV_NESTED_DIRECT_FLUSH}
        },
        .dependencies = BIT(HYPERV_FEAT_VAPIC)
    },
};

/******************************************************************************/

const char* hyperv_feature_macro[] = {
    "HYPERV_FEAT_RELAXED",
    "HYPERV_FEAT_VAPIC",
    "HYPERV_FEAT_TIME",
    "HYPERV_FEAT_CRASH",
    "HYPERV_FEAT_RESET",
    "HYPERV_FEAT_VPINDEX",
    "HYPERV_FEAT_RUNTIME",
    "HYPERV_FEAT_SYNIC",
    "HYPERV_FEAT_STIMER",
    "HYPERV_FEAT_FREQUENCIES",
    "HYPERV_FEAT_REENLIGHTENMENT",
    "HYPERV_FEAT_TLBFLUSH",
    "HYPERV_FEAT_EVMCS",
    "HYPERV_FEAT_IPI",
    "HYPERV_FEAT_STIMER_DIRECT",
    "HYPERV_FEAT_AVIC",
    "HYPERV_FEAT_SYNDBG",
    "HYPERV_FEAT_MSR_BITMAP",
    "HYPERV_FEAT_XMM_INPUT",
    "HYPERV_FEAT_TLBFLUSH_EXT",
    "HYPERV_FEAT_TLBFLUSH_DIRECT",
};

int main(void) {
    for (int i = 0; i < sizeof(hyperv_feature_macro) / sizeof(hyperv_feature_macro[0]); ++i) {
        bool feature = true;
        for (int j = 0; j < 2; ++j) {
            int gpr[4];
            if (kvm_hyperv_properties[i].flags[j].func == 0) break;
            __cpuid(gpr, kvm_hyperv_properties[i].flags[j].func);
            if ((gpr[kvm_hyperv_properties[i].flags[j].reg] & kvm_hyperv_properties[i].flags[j].bits) != kvm_hyperv_properties[i].flags[j].bits) {
                feature = false;
                break;
            }
        }
        printf("%c %-27s %s\n", feature ? '+' : '-', hyperv_feature_macro[i], kvm_hyperv_properties[i].desc);
    }
    return 0;
}