Have them be a machine option instead of a CPU one, to have something available, even if not ideal...

The existing Hyper-V enlightenments configuration mechanism is part of per-CPU configuration, which happens too late for this.

Signed-off-by: Mohamed Mediouni <mohamed@unpredictable.fr>
---
 accel/whpx/whpx-common.c       | 44 ++++++++++++++++++++++++++++++++++
 include/system/whpx-internal.h |  4 ++++
 target/i386/whpx/whpx-all.c    | 20 +++++++++-------
 3 files changed, 59 insertions(+), 9 deletions(-)

diff --git a/accel/whpx/whpx-common.c b/accel/whpx/whpx-common.c
index 4863fc8663..dae9ff0800 100644
--- a/accel/whpx/whpx-common.c
+++ b/accel/whpx/whpx-common.c
@@ -25,6 +25,7 @@
 #include "qapi/qapi-visit-common.h"
 #include "migration/blocker.h"
 #include "accel/accel-cpu-target.h"
+#include "qemu/target-info.h"
 #include <winerror.h>
 
 #include "system/whpx-internal.h"
@@ -470,6 +471,41 @@ static void whpx_set_kernel_irqchip(Object *obj, Visitor *v,
     }
 }
 
+static void whpx_set_hyperv(Object *obj, Visitor *v,
+                                   const char *name, void *opaque,
+                                   Error **errp)
+{
+    struct whpx_state *whpx = &whpx_global;
+    OnOffAuto mode;
+
+    if (!visit_type_OnOffAuto(v, name, &mode, errp)) {
+        return;
+    }
+
+    switch (mode) {
+    case ON_OFF_AUTO_ON:
+        whpx->hyperv_enlightenments_allowed = true;
+        whpx->hyperv_enlightenments_required = true;
+        break;
+
+    case ON_OFF_AUTO_OFF:
+        whpx->hyperv_enlightenments_allowed = false;
+        whpx->hyperv_enlightenments_required = false;
+        break;
+
+    case ON_OFF_AUTO_AUTO:
+        whpx->hyperv_enlightenments_allowed = true;
+        whpx->hyperv_enlightenments_required = false;
+        break;
+    default:
+        /*
+         * The value was checked in visit_type_OnOffAuto() above. If
+         * we get here, then something is wrong in QEMU.
+         */
+        abort();
+    }
+}
+
 static void whpx_cpu_accel_class_init(ObjectClass *oc, const void *data)
 {
     AccelCPUClass *acc = ACCEL_CPU_CLASS(oc);
@@ -498,6 +534,11 @@ static void whpx_accel_class_init(ObjectClass *oc, const void *data)
         NULL, NULL);
     object_class_property_set_description(oc, "kernel-irqchip",
         "Configure WHPX in-kernel irqchip");
+    object_class_property_add(oc, "hyperv", "OnOffAuto",
+        NULL, whpx_set_hyperv,
+        NULL, NULL);
+    object_class_property_set_description(oc, "hyperv",
+        "Configure Hyper-V enlightenments");
 }
 
 static void whpx_accel_instance_init(Object *obj)
@@ -507,6 +548,9 @@ static void whpx_accel_instance_init(Object *obj)
     memset(whpx, 0, sizeof(struct whpx_state));
     /* Turn on kernel-irqchip, by default */
     whpx->kernel_irqchip_allowed = true;
+
+    whpx->hyperv_enlightenments_allowed = true;
+    whpx->hyperv_enlightenments_required = false;
 }
 
 static const TypeInfo whpx_accel_type = {
diff --git a/include/system/whpx-internal.h b/include/system/whpx-internal.h
index 7a1c9871f1..8482901f71 100644
--- a/include/system/whpx-internal.h
+++ b/include/system/whpx-internal.h
@@ -42,6 +42,10 @@ struct whpx_state {
 
     bool kernel_irqchip_allowed;
     bool kernel_irqchip_required;
+
+    bool hyperv_enlightenments_allowed;
+    bool hyperv_enlightenments_required;
+
 };
 
 extern struct whpx_state whpx_global;
diff --git a/target/i386/whpx/whpx-all.c b/target/i386/whpx/whpx-all.c
index bc82995b33..b095c96962 100644
--- a/target/i386/whpx/whpx-all.c
+++ b/target/i386/whpx/whpx-all.c
@@ -2232,15 +2232,17 @@ int whpx_accel_init(AccelState *as, MachineState *ms)
         synthetic_features.Bank0.DirectSyntheticTimers = 1;
     }
 
-    hr = whp_dispatch.WHvSetPartitionProperty(
-            whpx->partition,
-            WHvPartitionPropertyCodeSyntheticProcessorFeaturesBanks,
-            &synthetic_features,
-            sizeof(WHV_SYNTHETIC_PROCESSOR_FEATURES_BANKS));
-    if (FAILED(hr)) {
-        error_report("WHPX: Failed to set synthetic features, hr=%08lx", hr);
-        ret = -EINVAL;
-        goto error;
+    if (whpx->hyperv_enlightenments_allowed) {
+        hr = whp_dispatch.WHvSetPartitionProperty(
+                whpx->partition,
+                WHvPartitionPropertyCodeSyntheticProcessorFeaturesBanks,
+                &synthetic_features,
+                sizeof(WHV_SYNTHETIC_PROCESSOR_FEATURES_BANKS));
+        if (FAILED(hr)) {
+            error_report("WHPX: Failed to set synthetic features, hr=%08lx", hr);
+            ret = -EINVAL;
+            goto error;
+        }
     }
 
     /* Register for MSR and CPUID exits */
-- 
2.50.1 (Apple Git-155)

On 7/3/26 16:41, Mohamed Mediouni wrote:
> Have them be a machine option instead of a CPU one, to have something available, even if not ideal...
> 
> The existing Hyper-V enlightenments configuration mechanism is part of per-CPU configuration, which happens too late for this.
> 
> Signed-off-by: Mohamed Mediouni <mohamed@unpredictable.fr>
> ---
>   accel/whpx/whpx-common.c       | 44 ++++++++++++++++++++++++++++++++++
>   include/system/whpx-internal.h |  4 ++++
>   target/i386/whpx/whpx-all.c    | 20 +++++++++-------
>   3 files changed, 59 insertions(+), 9 deletions(-)
> 
> diff --git a/accel/whpx/whpx-common.c b/accel/whpx/whpx-common.c
> index 4863fc8663..dae9ff0800 100644
> --- a/accel/whpx/whpx-common.c
> +++ b/accel/whpx/whpx-common.c
> @@ -25,6 +25,7 @@
>   #include "qapi/qapi-visit-common.h"
>   #include "migration/blocker.h"
>   #include "accel/accel-cpu-target.h"
> +#include "qemu/target-info.h"

I suppose you meant "qapi/qapi-types-common.h"?

>   #include <winerror.h>
>   
>   #include "system/whpx-internal.h"
> @@ -470,6 +471,41 @@ static void whpx_set_kernel_irqchip(Object *obj, Visitor *v,
>       }
>   }
>   
> +static void whpx_set_hyperv(Object *obj, Visitor *v,
> +                                   const char *name, void *opaque,
> +                                   Error **errp)
> +{
> +    struct whpx_state *whpx = &whpx_global;
> +    OnOffAuto mode;
> +
> +    if (!visit_type_OnOffAuto(v, name, &mode, errp)) {
> +        return;
> +    }
> +
> +    switch (mode) {
> +    case ON_OFF_AUTO_ON:
> +        whpx->hyperv_enlightenments_allowed = true;
> +        whpx->hyperv_enlightenments_required = true;
> +        break;
> +
> +    case ON_OFF_AUTO_OFF:
> +        whpx->hyperv_enlightenments_allowed = false;
> +        whpx->hyperv_enlightenments_required = false;
> +        break;
> +
> +    case ON_OFF_AUTO_AUTO:
> +        whpx->hyperv_enlightenments_allowed = true;
> +        whpx->hyperv_enlightenments_required = false;
> +        break;
> +    default:
> +        /*
> +         * The value was checked in visit_type_OnOffAuto() above. If
> +         * we get here, then something is wrong in QEMU.
> +         */
> +        abort();
> +    }
> +}
> +
>   static void whpx_cpu_accel_class_init(ObjectClass *oc, const void *data)
>   {
>       AccelCPUClass *acc = ACCEL_CPU_CLASS(oc);
> @@ -498,6 +534,11 @@ static void whpx_accel_class_init(ObjectClass *oc, const void *data)
>           NULL, NULL);
>       object_class_property_set_description(oc, "kernel-irqchip",
>           "Configure WHPX in-kernel irqchip");
> +    object_class_property_add(oc, "hyperv", "OnOffAuto",
> +        NULL, whpx_set_hyperv,
> +        NULL, NULL);
> +    object_class_property_set_description(oc, "hyperv",
> +        "Configure Hyper-V enlightenments");
>   }
>   
>   static void whpx_accel_instance_init(Object *obj)
> @@ -507,6 +548,9 @@ static void whpx_accel_instance_init(Object *obj)
>       memset(whpx, 0, sizeof(struct whpx_state));
>       /* Turn on kernel-irqchip, by default */
>       whpx->kernel_irqchip_allowed = true;
> +
> +    whpx->hyperv_enlightenments_allowed = true;
> +    whpx->hyperv_enlightenments_required = false;
>   }

> On 7. Mar 2026, at 16:53, Philippe Mathieu-Daudé <philmd@linaro.org> wrote:
> 
> On 7/3/26 16:41, Mohamed Mediouni wrote:
>> Have them be a machine option instead of a CPU one, to have something available, even if not ideal...
>> The existing Hyper-V enlightenments configuration mechanism is part of per-CPU configuration, which happens too late for this.
>> Signed-off-by: Mohamed Mediouni <mohamed@unpredictable.fr>
>> ---
>>  accel/whpx/whpx-common.c       | 44 ++++++++++++++++++++++++++++++++++
>>  include/system/whpx-internal.h |  4 ++++
>>  target/i386/whpx/whpx-all.c    | 20 +++++++++-------
>>  3 files changed, 59 insertions(+), 9 deletions(-)
>> diff --git a/accel/whpx/whpx-common.c b/accel/whpx/whpx-common.c
>> index 4863fc8663..dae9ff0800 100644
>> --- a/accel/whpx/whpx-common.c
>> +++ b/accel/whpx/whpx-common.c
>> @@ -25,6 +25,7 @@
>>  #include "qapi/qapi-visit-common.h"
>>  #include "migration/blocker.h"
>>  #include "accel/accel-cpu-target.h"
>> +#include "qemu/target-info.h"
> 
> I suppose you meant "qapi/qapi-types-common.h”?

Skipping including the line at all :)

Context: in an earlier iteration added an arch check added here with using the target_aarch64() function*,
but changed it for this rev.

* at the end, decided to use a bifurcated hyperv_enlightenments_allowed/hyperv_enlightenments_required
design like for kernel-irqchip, with enlightenments off by default on arm64 but on by default for x86, because 
arm64 virt is cleaner architecturally by enough that enlightenments don’t really matter there.

> 
>>  #include <winerror.h>
>>    #include "system/whpx-internal.h"
>> @@ -470,6 +471,41 @@ static void whpx_set_kernel_irqchip(Object *obj, Visitor *v,
>>      }
>>  }
>>  +static void whpx_set_hyperv(Object *obj, Visitor *v,
>> +                                   const char *name, void *opaque,
>> +                                   Error **errp)
>> +{
>> +    struct whpx_state *whpx = &whpx_global;
>> +    OnOffAuto mode;
>> +
>> +    if (!visit_type_OnOffAuto(v, name, &mode, errp)) {
>> +        return;
>> +    }
>> +
>> +    switch (mode) {
>> +    case ON_OFF_AUTO_ON:
>> +        whpx->hyperv_enlightenments_allowed = true;
>> +        whpx->hyperv_enlightenments_required = true;
>> +        break;
>> +
>> +    case ON_OFF_AUTO_OFF:
>> +        whpx->hyperv_enlightenments_allowed = false;
>> +        whpx->hyperv_enlightenments_required = false;
>> +        break;
>> +
>> +    case ON_OFF_AUTO_AUTO:
>> +        whpx->hyperv_enlightenments_allowed = true;
>> +        whpx->hyperv_enlightenments_required = false;
>> +        break;
>> +    default:
>> +        /*
>> +         * The value was checked in visit_type_OnOffAuto() above. If
>> +         * we get here, then something is wrong in QEMU.
>> +         */
>> +        abort();
>> +    }
>> +}
>> +
>>  static void whpx_cpu_accel_class_init(ObjectClass *oc, const void *data)
>>  {
>>      AccelCPUClass *acc = ACCEL_CPU_CLASS(oc);
>> @@ -498,6 +534,11 @@ static void whpx_accel_class_init(ObjectClass *oc, const void *data)
>>          NULL, NULL);
>>      object_class_property_set_description(oc, "kernel-irqchip",
>>          "Configure WHPX in-kernel irqchip");
>> +    object_class_property_add(oc, "hyperv", "OnOffAuto",
>> +        NULL, whpx_set_hyperv,
>> +        NULL, NULL);
>> +    object_class_property_set_description(oc, "hyperv",
>> +        "Configure Hyper-V enlightenments");
>>  }
>>    static void whpx_accel_instance_init(Object *obj)
>> @@ -507,6 +548,9 @@ static void whpx_accel_instance_init(Object *obj)
>>      memset(whpx, 0, sizeof(struct whpx_state));
>>      /* Turn on kernel-irqchip, by default */
>>      whpx->kernel_irqchip_allowed = true;
>> +
>> +    whpx->hyperv_enlightenments_allowed = true;
>> +    whpx->hyperv_enlightenments_required = false;
>>  }
>