Windows 10 doesn't have the API for this, so using this
only for Windows 11.

Signed-off-by: Mohamed Mediouni <mohamed@unpredictable.fr>
---
 include/system/whpx-internal.h |  3 ++
 target/i386/cpu.c              | 25 ++++++++++++
 target/i386/whpx/whpx-all.c    | 69 +++++++++++++++++++++++++++++++++-
 target/i386/whpx/whpx-i386.h   |  4 ++
 4 files changed, 100 insertions(+), 1 deletion(-)
 create mode 100644 target/i386/whpx/whpx-i386.h

diff --git a/include/system/whpx-internal.h b/include/system/whpx-internal.h
index 8482901f71..18fa792ac7 100644
--- a/include/system/whpx-internal.h
+++ b/include/system/whpx-internal.h
@@ -89,6 +89,9 @@ void whpx_apic_get(APICCommonState *s);
          UINT32 StateSize)) \
   X(HRESULT, WHvResetPartition, \
         (WHV_PARTITION_HANDLE Partition)) \
+  X(HRESULT, WHvGetVirtualProcessorCpuidOutput, \
+        (WHV_PARTITION_HANDLE Partition, UINT32 VpIndex, UINT32 Eax, \
+         UINT32 Ecx, WHV_CPUID_OUTPUT *CpuidOutput))
 
 #define WHP_DEFINE_TYPE(return_type, function_name, signature) \
     typedef return_type (WINAPI *function_name ## _t) signature;
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index c6fd1dc00e..0000093fa3 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -26,6 +26,8 @@
 #include "tcg/helper-tcg.h"
 #include "exec/translation-block.h"
 #include "system/hvf.h"
+#include "system/whpx.h"
+#include "whpx/whpx-i386.h"
 #include "hvf/hvf-i386.h"
 #include "kvm/kvm_i386.h"
 #include "kvm/tdx.h"
@@ -8087,6 +8089,17 @@ uint64_t x86_cpu_get_supported_feature_word(X86CPU *cpu, FeatureWord w)
         r = hvf_get_supported_cpuid(wi->cpuid.eax,
                                     wi->cpuid.ecx,
                                     wi->cpuid.reg);
+    } else if (whpx_enabled()) {
+        if (wi->type != CPUID_FEATURE_WORD) {
+            return 0;
+        }
+        if (whpx_is_legacy_os()) {
+            r = wi->tcg_features;
+        } else {
+            r = whpx_get_supported_cpuid(wi->cpuid.eax,
+                                        wi->cpuid.ecx,
+                                        wi->cpuid.reg);
+        }
     } else if (tcg_enabled() || qtest_enabled()) {
         r = wi->tcg_features;
     } else {
@@ -8168,6 +8181,18 @@ static void x86_cpu_get_supported_cpuid(uint32_t func, uint32_t index,
         *ebx = hvf_get_supported_cpuid(func, index, R_EBX);
         *ecx = hvf_get_supported_cpuid(func, index, R_ECX);
         *edx = hvf_get_supported_cpuid(func, index, R_EDX);
+    } else if (whpx_enabled()) {
+        if (whpx_is_legacy_os()) {
+            *eax = 0;
+            *ebx = 0;
+            *ecx = 0;
+            *edx = 0;
+        } else {
+            *eax = whpx_get_supported_cpuid(func, index, R_EAX);
+            *ebx = whpx_get_supported_cpuid(func, index, R_EBX);
+            *ecx = whpx_get_supported_cpuid(func, index, R_ECX);
+            *edx = whpx_get_supported_cpuid(func, index, R_EDX);
+        }
     } else {
         *eax = 0;
         *ebx = 0;
diff --git a/target/i386/whpx/whpx-all.c b/target/i386/whpx/whpx-all.c
index 4127440c0c..ee44e4e060 100644
--- a/target/i386/whpx/whpx-all.c
+++ b/target/i386/whpx/whpx-all.c
@@ -36,6 +36,7 @@
 #include "system/whpx-accel-ops.h"
 #include "system/whpx-all.h"
 #include "system/whpx-common.h"
+#include "whpx-i386.h"
 
 #include "emulate/x86_decode.h"
 #include "emulate/x86_emu.h"
@@ -49,6 +50,8 @@
 /* for kernel-irqchip=off */
 #define HV_X64_MSR_APIC_FREQUENCY       0x40000023
 
+static bool is_legacy_os = false;
+
 static const WHV_REGISTER_NAME whpx_register_names[] = {
 
     /* X64 General purpose registers */
@@ -1062,6 +1065,71 @@ static void whpx_init_emu(void)
     init_emu(&whpx_x86_emul_ops);
 }
 
+bool whpx_is_legacy_os(void)
+{
+    return is_legacy_os;
+}
+
+uint32_t whpx_get_supported_cpuid(uint32_t func, uint32_t idx, int reg)
+{
+    WHV_CPUID_OUTPUT output;
+    uint32_t eax, ebx, ecx, edx;
+    uint32_t cpu_index = 0;
+    bool temp_cpu = true;
+    HRESULT hr;
+
+    hr = whp_dispatch.WHvCreateVirtualProcessor(
+        whpx_global.partition, cpu_index, 0);
+
+    /* This means that the CPU already exists... */
+    if (FAILED(hr)) {
+        temp_cpu = false;
+    }
+
+    hr = whp_dispatch.WHvGetVirtualProcessorCpuidOutput(whpx_global.partition,
+        cpu_index, func, idx, &output);
+
+    if (FAILED(hr)) {
+        abort();
+    }
+
+    if (temp_cpu) {
+        hr = whp_dispatch.WHvDeleteVirtualProcessor(whpx_global.partition, cpu_index);
+        if (FAILED(hr)) {
+            abort();
+        }
+    }
+
+    eax = output.Eax;
+    ebx = output.Ebx;
+    ecx = output.Ecx;
+    edx = output.Edx;
+
+    /*
+     * We can emulate X2APIC even for the kernel-irqchip=off case.
+     * CPUID_EXT_HYPERVISOR and CPUID_HT should be considered present
+     * always, so report them as unconditionally supported here.
+     */
+    if (func == 1) {
+        ecx |= CPUID_EXT_X2APIC;
+        ecx |= CPUID_EXT_HYPERVISOR;
+        edx |= CPUID_HT;
+    }
+
+    switch (reg) {
+    case R_EAX:
+        return eax;
+    case R_EBX:
+        return ebx;
+    case R_ECX:
+        return ecx;
+    case R_EDX:
+        return edx;
+    default:
+        return 0;
+    }
+}
+
 /*
  * Controls whether we should intercept various exceptions on the guest,
  * namely breakpoint/single-step events.
@@ -2235,7 +2303,6 @@ int whpx_accel_init(AccelState *as, MachineState *ms)
     WHV_CAPABILITY_FEATURES features = {0};
     WHV_PROCESSOR_FEATURES_BANKS processor_features;
     WHV_PROCESSOR_PERFMON_FEATURES perfmon_features;
-    bool is_legacy_os = false;
     UINT32 cpuidExitList[] = {1};
 
     whpx = &whpx_global;
diff --git a/target/i386/whpx/whpx-i386.h b/target/i386/whpx/whpx-i386.h
new file mode 100644
index 0000000000..6db9a75d39
--- /dev/null
+++ b/target/i386/whpx/whpx-i386.h
@@ -0,0 +1,4 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+uint32_t whpx_get_supported_cpuid(uint32_t func, uint32_t idx, int reg);
+bool whpx_is_legacy_os(void);
-- 
2.50.1 (Apple Git-155)