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-rw-r--r--include/hw/i386/pc.h5
-rw-r--r--target/i386/cpu.c14
-rw-r--r--target/i386/cpu.h2
-rw-r--r--target/i386/kvm.c3
4 files changed, 23 insertions, 1 deletions
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index 8226904524..087d184ef5 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -371,6 +371,11 @@ bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);
 
 #define PC_COMPAT_2_10 \
     HW_COMPAT_2_10 \
+    {\
+        .driver   = TYPE_X86_CPU,\
+        .property = "x-hv-max-vps",\
+        .value    = "0x40",\
+    },
 
 #define PC_COMPAT_2_9 \
     HW_COMPAT_2_9 \
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 7644f6dc2c..40c3091edf 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -4145,6 +4145,20 @@ static Property x86_cpu_properties[] = {
                      false),
     DEFINE_PROP_BOOL("vmware-cpuid-freq", X86CPU, vmware_cpuid_freq, true),
     DEFINE_PROP_BOOL("tcg-cpuid", X86CPU, expose_tcg, true),
+
+    /*
+     * From "Requirements for Implementing the Microsoft
+     * Hypervisor Interface":
+     * https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/reference/tlfs
+     *
+     * "Starting with Windows Server 2012 and Windows 8, if
+     * CPUID.40000005.EAX contains a value of -1, Windows assumes that
+     * the hypervisor imposes no specific limit to the number of VPs.
+     * In this case, Windows Server 2012 guest VMs may use more than
+     * 64 VPs, up to the maximum supported number of processors applicable
+     * to the specific Windows version being used."
+     */
+    DEFINE_PROP_INT32("x-hv-max-vps", X86CPU, hv_max_vps, -1),
     DEFINE_PROP_END_OF_LIST()
 };
 
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 525d35d836..5c726f3e4b 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1282,6 +1282,8 @@ struct X86CPU {
     int32_t socket_id;
     int32_t core_id;
     int32_t thread_id;
+
+    int32_t hv_max_vps;
 };
 
 static inline X86CPU *x86_env_get_cpu(CPUX86State *env)
diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index 739334a5a6..ee4e91fa64 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -786,7 +786,8 @@ int kvm_arch_init_vcpu(CPUState *cs)
 
         c = &cpuid_data.entries[cpuid_i++];
         c->function = HYPERV_CPUID_IMPLEMENT_LIMITS;
-        c->eax = 0x40;
+
+        c->eax = cpu->hv_max_vps;
         c->ebx = 0x40;
 
         kvm_base = KVM_CPUID_SIGNATURE_NEXT;