Merge remote-tracking branch 'remotes/ehabkost-gl/tags/x86-next-pull-request' into staging

x86 queue, 2021-07-13

Bug fixes:
* numa: Parse initiator= attribute before cpus= attribute
  (Michal Privoznik)
* Fix CPUID level for AMD (Zhenwei Pi)
* Suppress CPUID leaves not defined by the CPU vendor
  (Michael Roth)

Cleanup:
* Hyper-V feature handling cleanup (Vitaly Kuznetsov)

# gpg: Signature made Tue 13 Jul 2021 17:09:01 BST
# gpg:                using RSA key 5A322FD5ABC4D3DBACCFD1AA2807936F984DC5A6
# gpg:                issuer "ehabkost@redhat.com"
# gpg: Good signature from "Eduardo Habkost <ehabkost@redhat.com>" [full]
# Primary key fingerprint: 5A32 2FD5 ABC4 D3DB ACCF  D1AA 2807 936F 984D C5A6

* remotes/ehabkost-gl/tags/x86-next-pull-request:
  numa: Parse initiator= attribute before cpus= attribute
  numa: Report expected initiator
  target/i386: Fix cpuid level for AMD
  target/i386: suppress CPUID leaves not defined by the CPU vendor
  i386: Hyper-V SynIC requires POST_MESSAGES/SIGNAL_EVENTS privileges
  i386: HV_HYPERCALL_AVAILABLE privilege bit is always needed
  i386: kill off hv_cpuid_check_and_set()
  i386: expand Hyper-V features during CPU feature expansion time
  i386: make hyperv_expand_features() return bool
  i386: hardcode supported eVMCS version to '1'
  i386: clarify 'hv-passthrough' behavior

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

10 files changed, 172 insertions, 111 deletions

diff --git a/docs/hyperv.txt b/docs/hyperv.txt
index e53c581f45..000638a2fd 100644
--- a/docs/hyperv.txt
+++ b/docs/hyperv.txt
@@ -170,7 +170,7 @@ Recommended: hv-frequencies
 3.16. hv-evmcs
 ===============
 The enlightenment is nested specific, it targets Hyper-V on KVM guests. When
-enabled, it provides Enlightened VMCS feature to the guest. The feature
+enabled, it provides Enlightened VMCS version 1 feature to the guest. The feature
 implements paravirtualized protocol between L0 (KVM) and L1 (Hyper-V)
 hypervisors making L2 exits to the hypervisor faster. The feature is Intel-only.
 Note: some virtualization features (e.g. Posted Interrupts) are disabled when
@@ -209,8 +209,11 @@ In some cases (e.g. during development) it may make sense to use QEMU in
 'pass-through' mode and give Windows guests all enlightenments currently
 supported by KVM. This pass-through mode is enabled by "hv-passthrough" CPU
 flag.
-Note: enabling this flag effectively prevents migration as supported features
-may differ between target and destination.
+Note: "hv-passthrough" flag only enables enlightenments which are known to QEMU
+(have corresponding "hv-*" flag) and copies "hv-spinlocks="/"hv-vendor-id="
+values from KVM to QEMU. "hv-passthrough" overrides all other "hv-*" settings on
+the command line. Also, enabling this flag effectively prevents migration as the
+list of enabled enlightenments may differ between target and destination hosts.
 
 
 4. Useful links
diff --git a/hw/core/machine.c b/hw/core/machine.c
index 57c18f909a..6f59fb0b7f 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -728,7 +728,8 @@ void machine_set_cpu_numa_node(MachineState *machine,
             if ((numa_info[props->node_id].initiator < MAX_NODES) &&
                 (props->node_id != numa_info[props->node_id].initiator)) {
                 error_setg(errp, "The initiator of CPU NUMA node %" PRId64
-                        " should be itself", props->node_id);
+                           " should be itself (got %" PRIu16 ")",
+                           props->node_id, numa_info[props->node_id].initiator);
                 return;
             }
             numa_info[props->node_id].has_cpu = true;
diff --git a/hw/core/numa.c b/hw/core/numa.c
index 1058d3697b..510d096a88 100644
--- a/hw/core/numa.c
+++ b/hw/core/numa.c
@@ -88,6 +88,29 @@ static void parse_numa_node(MachineState *ms, NumaNodeOptions *node,
         return;
     }
 
+    /*
+     * If not set the initiator, set it to MAX_NODES. And if
+     * HMAT is enabled and this node has no cpus, QEMU will raise error.
+     */
+    numa_info[nodenr].initiator = MAX_NODES;
+    if (node->has_initiator) {
+        if (!ms->numa_state->hmat_enabled) {
+            error_setg(errp, "ACPI Heterogeneous Memory Attribute Table "
+                       "(HMAT) is disabled, enable it with -machine hmat=on "
+                       "before using any of hmat specific options");
+            return;
+        }
+
+        if (node->initiator >= MAX_NODES) {
+            error_report("The initiator id %" PRIu16 " expects an integer "
+                         "between 0 and %d", node->initiator,
+                         MAX_NODES - 1);
+            return;
+        }
+
+        numa_info[nodenr].initiator = node->initiator;
+    }
+
     for (cpus = node->cpus; cpus; cpus = cpus->next) {
         CpuInstanceProperties props;
         if (cpus->value >= max_cpus) {
@@ -142,28 +165,6 @@ static void parse_numa_node(MachineState *ms, NumaNodeOptions *node,
         numa_info[nodenr].node_memdev = MEMORY_BACKEND(o);
     }
 
-    /*
-     * If not set the initiator, set it to MAX_NODES. And if
-     * HMAT is enabled and this node has no cpus, QEMU will raise error.
-     */
-    numa_info[nodenr].initiator = MAX_NODES;
-    if (node->has_initiator) {
-        if (!ms->numa_state->hmat_enabled) {
-            error_setg(errp, "ACPI Heterogeneous Memory Attribute Table "
-                       "(HMAT) is disabled, enable it with -machine hmat=on "
-                       "before using any of hmat specific options");
-            return;
-        }
-
-        if (node->initiator >= MAX_NODES) {
-            error_report("The initiator id %" PRIu16 " expects an integer "
-                         "between 0 and %d", node->initiator,
-                         MAX_NODES - 1);
-            return;
-        }
-
-        numa_info[nodenr].initiator = node->initiator;
-    }
     numa_info[nodenr].present = true;
     max_numa_nodeid = MAX(max_numa_nodeid, nodenr + 1);
     ms->numa_state->num_nodes++;
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 8e1220db72..aa79c5e0e6 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -98,6 +98,7 @@ GlobalProperty pc_compat_6_0[] = {
     { "qemu64" "-" TYPE_X86_CPU, "family", "6" },
     { "qemu64" "-" TYPE_X86_CPU, "model", "6" },
     { "qemu64" "-" TYPE_X86_CPU, "stepping", "3" },
+    { TYPE_X86_CPU, "x-vendor-cpuid-only", "off" },
 };
 const size_t pc_compat_6_0_len = G_N_ELEMENTS(pc_compat_6_0);
 
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 5f595a0d7e..48b55ebd0a 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -5155,6 +5155,9 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
         if (cpu->cache_info_passthrough) {
             host_cpuid(index, 0, eax, ebx, ecx, edx);
             break;
+        } else if (cpu->vendor_cpuid_only && IS_AMD_CPU(env)) {
+            *eax = *ebx = *ecx = *edx = 0;
+            break;
         }
         *eax = 1; /* Number of CPUID[EAX=2] calls required */
         *ebx = 0;
@@ -5176,6 +5179,8 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
             if ((*eax & 31) && cs->nr_cores > 1) {
                 *eax |= (cs->nr_cores - 1) << 26;
             }
+        } else if (cpu->vendor_cpuid_only && IS_AMD_CPU(env)) {
+            *eax = *ebx = *ecx = *edx = 0;
         } else {
             *eax = 0;
             switch (count) {
@@ -5945,8 +5950,15 @@ void x86_cpu_expand_features(X86CPU *cpu, Error **errp)
             }
         }
 
-        /* CPU topology with multi-dies support requires CPUID[0x1F] */
-        if (env->nr_dies > 1) {
+        /*
+         * Intel CPU topology with multi-dies support requires CPUID[0x1F].
+         * For AMD Rome/Milan, cpuid level is 0x10, and guest OS should detect
+         * extended toplogy by leaf 0xB. Only adjust it for Intel CPU, unless
+         * cpu->vendor_cpuid_only has been unset for compatibility with older
+         * machine types.
+         */
+        if ((env->nr_dies > 1) &&
+            (IS_INTEL_CPU(env) || !cpu->vendor_cpuid_only)) {
             x86_cpu_adjust_level(cpu, &env->cpuid_min_level, 0x1F);
         }
 
@@ -5974,6 +5986,10 @@ void x86_cpu_expand_features(X86CPU *cpu, Error **errp)
     if (env->cpuid_xlevel2 == UINT32_MAX) {
         env->cpuid_xlevel2 = env->cpuid_min_xlevel2;
     }
+
+    if (kvm_enabled()) {
+        kvm_hyperv_expand_features(cpu, errp);
+    }
 }
 
 /*
@@ -6647,6 +6663,7 @@ static Property x86_cpu_properties[] = {
     DEFINE_PROP_BOOL("full-cpuid-auto-level", X86CPU, full_cpuid_auto_level, true),
     DEFINE_PROP_STRING("hv-vendor-id", X86CPU, hyperv_vendor),
     DEFINE_PROP_BOOL("cpuid-0xb", X86CPU, enable_cpuid_0xb, true),
+    DEFINE_PROP_BOOL("x-vendor-cpuid-only", X86CPU, vendor_cpuid_only, true),
     DEFINE_PROP_BOOL("lmce", X86CPU, enable_lmce, false),
     DEFINE_PROP_BOOL("l3-cache", X86CPU, enable_l3_cache, true),
     DEFINE_PROP_BOOL("kvm-no-smi-migration", X86CPU, kvm_no_smi_migration,
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 8f3747dd28..950a991a71 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1748,6 +1748,9 @@ struct X86CPU {
     /* Enable auto level-increase for all CPUID leaves */
     bool full_cpuid_auto_level;
 
+    /* Only advertise CPUID leaves defined by the vendor */
+    bool vendor_cpuid_only;
+
     /* Enable auto level-increase for Intel Processor Trace leave */
     bool intel_pt_auto_level;
 
diff --git a/target/i386/kvm/hyperv-proto.h b/target/i386/kvm/hyperv-proto.h
index e30d64b4ad..5fbb385cc1 100644
--- a/target/i386/kvm/hyperv-proto.h
+++ b/target/i386/kvm/hyperv-proto.h
@@ -39,6 +39,12 @@
 #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)
diff --git a/target/i386/kvm/kvm-stub.c b/target/i386/kvm/kvm-stub.c
index 92f49121b8..f6e7e4466e 100644
--- a/target/i386/kvm/kvm-stub.c
+++ b/target/i386/kvm/kvm-stub.c
@@ -39,3 +39,8 @@ bool kvm_hv_vpindex_settable(void)
 {
     return false;
 }
+
+bool kvm_hyperv_expand_features(X86CPU *cpu, Error **errp)
+{
+    abort();
+}
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index a85035492f..59ed8327ac 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -813,8 +813,6 @@ static struct {
     [HYPERV_FEAT_RELAXED] = {
         .desc = "relaxed timing (hv-relaxed)",
         .flags = {
-            {.func = HV_CPUID_FEATURES, .reg = R_EAX,
-             .bits = HV_HYPERCALL_AVAILABLE},
             {.func = HV_CPUID_ENLIGHTMENT_INFO, .reg = R_EAX,
              .bits = HV_RELAXED_TIMING_RECOMMENDED}
         }
@@ -823,7 +821,7 @@ static struct {
         .desc = "virtual APIC (hv-vapic)",
         .flags = {
             {.func = HV_CPUID_FEATURES, .reg = R_EAX,
-             .bits = HV_HYPERCALL_AVAILABLE | HV_APIC_ACCESS_AVAILABLE},
+             .bits = HV_APIC_ACCESS_AVAILABLE},
             {.func = HV_CPUID_ENLIGHTMENT_INFO, .reg = R_EAX,
              .bits = HV_APIC_ACCESS_RECOMMENDED}
         }
@@ -832,8 +830,7 @@ static struct {
         .desc = "clocksources (hv-time)",
         .flags = {
             {.func = HV_CPUID_FEATURES, .reg = R_EAX,
-             .bits = HV_HYPERCALL_AVAILABLE | HV_TIME_REF_COUNT_AVAILABLE |
-             HV_REFERENCE_TSC_AVAILABLE}
+             .bits = HV_TIME_REF_COUNT_AVAILABLE | HV_REFERENCE_TSC_AVAILABLE}
         }
     },
     [HYPERV_FEAT_CRASH] = {
@@ -1148,16 +1145,12 @@ static bool hyperv_feature_supported(CPUState *cs, int feature)
     return true;
 }
 
-static int hv_cpuid_check_and_set(CPUState *cs, int feature, Error **errp)
+/* Checks that all feature dependencies are enabled */
+static bool hv_feature_check_deps(X86CPU *cpu, int feature, Error **errp)
 {
-    X86CPU *cpu = X86_CPU(cs);
     uint64_t deps;
     int dep_feat;
 
-    if (!hyperv_feat_enabled(cpu, feature) && !cpu->hyperv_passthrough) {
-        return 0;
-    }
-
     deps = kvm_hyperv_properties[feature].dependencies;
     while (deps) {
         dep_feat = ctz64(deps);
@@ -1165,26 +1158,12 @@ static int hv_cpuid_check_and_set(CPUState *cs, int feature, Error **errp)
             error_setg(errp, "Hyper-V %s requires Hyper-V %s",
                        kvm_hyperv_properties[feature].desc,
                        kvm_hyperv_properties[dep_feat].desc);
-            return 1;
+            return false;
         }
         deps &= ~(1ull << dep_feat);
     }
 
-    if (!hyperv_feature_supported(cs, feature)) {
-        if (hyperv_feat_enabled(cpu, feature)) {
-            error_setg(errp, "Hyper-V %s is not supported by kernel",
-                       kvm_hyperv_properties[feature].desc);
-            return 1;
-        } else {
-            return 0;
-        }
-    }
-
-    if (cpu->hyperv_passthrough) {
-        cpu->hyperv_features |= BIT(feature);
-    }
-
-    return 0;
+    return true;
 }
 
 static uint32_t hv_build_cpuid_leaf(CPUState *cs, uint32_t func, int reg)
@@ -1220,12 +1199,23 @@ static uint32_t hv_build_cpuid_leaf(CPUState *cs, uint32_t func, int reg)
  * of 'hv_passthrough' mode and fills the environment with all supported
  * Hyper-V features.
  */
-static void hyperv_expand_features(CPUState *cs, Error **errp)
+bool kvm_hyperv_expand_features(X86CPU *cpu, Error **errp)
 {
-    X86CPU *cpu = X86_CPU(cs);
+    CPUState *cs = CPU(cpu);
+    Error *local_err = NULL;
+    int feat;
 
     if (!hyperv_enabled(cpu))
-        return;
+        return true;
+
+    /*
+     * When kvm_hyperv_expand_features is called at CPU feature expansion
+     * time per-CPU kvm_state is not available yet so we can only proceed
+     * when KVM_CAP_SYS_HYPERV_CPUID is supported.
+     */
+    if (!cs->kvm_state &&
+        !kvm_check_extension(kvm_state, KVM_CAP_SYS_HYPERV_CPUID))
+        return true;
 
     if (cpu->hyperv_passthrough) {
         cpu->hyperv_vendor_id[0] =
@@ -1269,53 +1259,37 @@ static void hyperv_expand_features(CPUState *cs, Error **errp)
 
         cpu->hyperv_spinlock_attempts =
             hv_cpuid_get_host(cs, HV_CPUID_ENLIGHTMENT_INFO, R_EBX);
-    }
 
-    /* Features */
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_RELAXED, errp)) {
-        return;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_VAPIC, errp)) {
-        return;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_TIME, errp)) {
-        return;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_CRASH, errp)) {
-        return;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_RESET, errp)) {
-        return;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_VPINDEX, errp)) {
-        return;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_RUNTIME, errp)) {
-        return;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_SYNIC, errp)) {
-        return;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_STIMER, errp)) {
-        return;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_FREQUENCIES, errp)) {
-        return;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_REENLIGHTENMENT, errp)) {
-        return;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_TLBFLUSH, errp)) {
-        return;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_EVMCS, errp)) {
-        return;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_IPI, errp)) {
-        return;
-    }
-    if (hv_cpuid_check_and_set(cs, HYPERV_FEAT_STIMER_DIRECT, errp)) {
-        return;
+        /*
+         * Mark feature as enabled in 'cpu->hyperv_features' as
+         * hv_build_cpuid_leaf() uses this info to build guest CPUIDs.
+         */
+        for (feat = 0; feat < ARRAY_SIZE(kvm_hyperv_properties); feat++) {
+            if (hyperv_feature_supported(cs, feat)) {
+                cpu->hyperv_features |= BIT(feat);
+            }
+        }
+    } else {
+        /* Check features availability and dependencies */
+        for (feat = 0; feat < ARRAY_SIZE(kvm_hyperv_properties); feat++) {
+            /* If the feature was not requested skip it. */
+            if (!hyperv_feat_enabled(cpu, feat)) {
+                continue;
+            }
+
+            /* Check if the feature is supported by KVM */
+            if (!hyperv_feature_supported(cs, feat)) {
+                error_setg(errp, "Hyper-V %s is not supported by kernel",
+                           kvm_hyperv_properties[feat].desc);
+                return false;
+            }
+
+            /* Check dependencies */
+            if (!hv_feature_check_deps(cpu, feat, &local_err)) {
+                error_propagate(errp, local_err);
+                return false;
+            }
+        }
     }
 
     /* Additional dependencies not covered by kvm_hyperv_properties[] */
@@ -1325,7 +1299,10 @@ static void hyperv_expand_features(CPUState *cs, Error **errp)
         error_setg(errp, "Hyper-V %s requires Hyper-V %s",
                    kvm_hyperv_properties[HYPERV_FEAT_SYNIC].desc,
                    kvm_hyperv_properties[HYPERV_FEAT_VPINDEX].desc);
+        return false;
     }
+
+    return true;
 }
 
 /*
@@ -1366,6 +1343,15 @@ static int hyperv_fill_cpuids(CPUState *cs,
     c->ebx = hv_build_cpuid_leaf(cs, HV_CPUID_FEATURES, R_EBX);
     c->edx = hv_build_cpuid_leaf(cs, HV_CPUID_FEATURES, R_EDX);
 
+    /* Unconditionally required with any Hyper-V enlightenment */
+    c->eax |= HV_HYPERCALL_AVAILABLE;
+
+    /* SynIC and Vmbus devices require messages/signals hypercalls */
+    if (hyperv_feat_enabled(cpu, HYPERV_FEAT_SYNIC) &&
+        !cpu->hyperv_synic_kvm_only) {
+        c->ebx |= HV_POST_MESSAGES | HV_SIGNAL_EVENTS;
+    }
+
     /* Not exposed by KVM but needed to make CPU hotplug in Windows work */
     c->edx |= HV_CPU_DYNAMIC_PARTITIONING_AVAILABLE;
 
@@ -1409,6 +1395,21 @@ static int hyperv_fill_cpuids(CPUState *cs,
 static Error *hv_passthrough_mig_blocker;
 static Error *hv_no_nonarch_cs_mig_blocker;
 
+/* Checks that the exposed eVMCS version range is supported by KVM */
+static bool evmcs_version_supported(uint16_t evmcs_version,
+                                    uint16_t supported_evmcs_version)
+{
+    uint8_t min_version = evmcs_version & 0xff;
+    uint8_t max_version = evmcs_version >> 8;
+    uint8_t min_supported_version = supported_evmcs_version & 0xff;
+    uint8_t max_supported_version = supported_evmcs_version >> 8;
+
+    return (min_version >= min_supported_version) &&
+        (max_version <= max_supported_version);
+}
+
+#define DEFAULT_EVMCS_VERSION ((1 << 8) | 1)
+
 static int hyperv_init_vcpu(X86CPU *cpu)
 {
     CPUState *cs = CPU(cpu);
@@ -1488,17 +1489,33 @@ static int hyperv_init_vcpu(X86CPU *cpu)
     }
 
     if (hyperv_feat_enabled(cpu, HYPERV_FEAT_EVMCS)) {
-        uint16_t evmcs_version;
+        uint16_t evmcs_version = DEFAULT_EVMCS_VERSION;
+        uint16_t supported_evmcs_version;
 
         ret = kvm_vcpu_enable_cap(cs, KVM_CAP_HYPERV_ENLIGHTENED_VMCS, 0,
-                                  (uintptr_t)&evmcs_version);
+                                  (uintptr_t)&supported_evmcs_version);
 
+        /*
+         * KVM is required to support EVMCS ver.1. as that's what 'hv-evmcs'
+         * option sets. Note: we hardcode the maximum supported eVMCS version
+         * to '1' as well so 'hv-evmcs' feature is migratable even when (and if)
+         * ver.2 is implemented. A new option (e.g. 'hv-evmcs=2') will then have
+         * to be added.
+         */
         if (ret < 0) {
-            fprintf(stderr, "Hyper-V %s is not supported by kernel\n",
-                    kvm_hyperv_properties[HYPERV_FEAT_EVMCS].desc);
+            error_report("Hyper-V %s is not supported by kernel",
+                         kvm_hyperv_properties[HYPERV_FEAT_EVMCS].desc);
             return ret;
         }
 
+        if (!evmcs_version_supported(evmcs_version, supported_evmcs_version)) {
+            error_report("eVMCS version range [%d..%d] is not supported by "
+                         "kernel (supported: [%d..%d])", evmcs_version & 0xff,
+                         evmcs_version >> 8, supported_evmcs_version & 0xff,
+                         supported_evmcs_version >> 8);
+            return -ENOTSUP;
+        }
+
         cpu->hyperv_nested[0] = evmcs_version;
     }
 
@@ -1559,9 +1576,15 @@ int kvm_arch_init_vcpu(CPUState *cs)
 
     env->apic_bus_freq = KVM_APIC_BUS_FREQUENCY;
 
-    /* Paravirtualization CPUIDs */
-    hyperv_expand_features(cs, &local_err);
-    if (local_err) {
+    /*
+     * kvm_hyperv_expand_features() is called here for the second time in case
+     * KVM_CAP_SYS_HYPERV_CPUID is not supported. While we can't possibly handle
+     * 'query-cpu-model-expansion' in this case as we don't have a KVM vCPU to
+     * check which Hyper-V enlightenments are supported and which are not, we
+     * can still proceed and check/expand Hyper-V enlightenments here so legacy
+     * behavior is preserved.
+     */
+    if (!kvm_hyperv_expand_features(cpu, &local_err)) {
         error_report_err(local_err);
         return -ENOSYS;
     }
diff --git a/target/i386/kvm/kvm_i386.h b/target/i386/kvm/kvm_i386.h
index dc72508389..54667b35f0 100644
--- a/target/i386/kvm/kvm_i386.h
+++ b/target/i386/kvm/kvm_i386.h
@@ -47,6 +47,7 @@ bool kvm_has_x2apic_api(void);
 bool kvm_has_waitpkg(void);
 
 bool kvm_hv_vpindex_settable(void);
+bool kvm_hyperv_expand_features(X86CPU *cpu, Error **errp);
 
 uint64_t kvm_swizzle_msi_ext_dest_id(uint64_t address);