[PULL 18/28] hw/arm, target/arm: nested virtualisation on HVF

[Peter Maydell <peter.maydell@linaro.org>]

From: Mohamed Mediouni <mohamed@unpredictable.fr>

Add hvf_arm_el2_supported for querying EL2 availability.
An hvf_nested_virt_enable workaround is added as nested virt has
to be enabled early on HVF.

And adds hvf_nested_virt_enabled.

Signed-off-by: Mohamed Mediouni <mohamed@unpredictable.fr>
Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Message-id: 20260429190532.26538-6-mohamed@unpredictable.fr
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 accel/hvf/hvf-all.c    |  6 ++++++
 accel/stubs/hvf-stub.c | 11 +++++++++++
 hw/arm/virt.c          |  5 +++++
 include/system/hvf.h   |  5 +++++
 target/arm/hvf/hvf.c   | 42 ++++++++++++++++++++++++++++++++++++++++--
 5 files changed, 67 insertions(+), 2 deletions(-)

diff --git a/accel/hvf/hvf-all.c b/accel/hvf/hvf-all.c
index add265e0c8..da29aa3aa3 100644
--- a/accel/hvf/hvf-all.c
+++ b/accel/hvf/hvf-all.c
@@ -24,6 +24,12 @@
 
 bool hvf_allowed;
 bool hvf_kernel_irqchip;
+bool hvf_nested_virt;
+
+void hvf_nested_virt_enable(bool nested_virt)
+{
+    hvf_nested_virt = nested_virt;
+}
 
 const char *hvf_return_string(hv_return_t ret)
 {
diff --git a/accel/stubs/hvf-stub.c b/accel/stubs/hvf-stub.c
index 6bd08759ba..7643e8c5f5 100644
--- a/accel/stubs/hvf-stub.c
+++ b/accel/stubs/hvf-stub.c
@@ -11,3 +11,14 @@
 
 bool hvf_allowed;
 bool hvf_kernel_irqchip;
+bool hvf_nested_virt;
+
+void hvf_nested_virt_enable(bool nested_virt)
+{
+    /*
+     * This is called unconditionally from hw/arm/virt.c
+     * because we don't know if HVF is going to be used
+     * as that step of initialisation happens later.
+     * As such, do nothing here instead of marking as unreachable.
+     */
+}
diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 47400214a2..ca50411020 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -2987,6 +2987,11 @@ static void virt_set_virt(Object *obj, bool value, Error **errp)
     VirtMachineState *vms = VIRT_MACHINE(obj);
 
     vms->virt = value;
+    /*
+     * At this point, HVF is not initialised yet.
+     * However, it needs to know if nested virt is enabled at init time.
+     */
+    hvf_nested_virt_enable(value);
 }
 
 static bool virt_get_highmem(Object *obj, Error **errp)
diff --git a/include/system/hvf.h b/include/system/hvf.h
index dc8da85979..a961df8b95 100644
--- a/include/system/hvf.h
+++ b/include/system/hvf.h
@@ -28,11 +28,16 @@ extern bool hvf_allowed;
 #define hvf_enabled() (hvf_allowed)
 extern bool hvf_kernel_irqchip;
 #define hvf_irqchip_in_kernel()  (hvf_kernel_irqchip)
+extern bool hvf_nested_virt;
+#define hvf_nested_virt_enabled()  (hvf_nested_virt)
 #else /* !CONFIG_HVF_IS_POSSIBLE */
 #define hvf_enabled() 0
 #define hvf_irqchip_in_kernel() 0
+#define hvf_nested_virt_enabled() 0
 #endif /* !CONFIG_HVF_IS_POSSIBLE */
 
+void hvf_nested_virt_enable(bool nested_virt);
+
 #define TYPE_HVF_ACCEL ACCEL_CLASS_NAME("hvf")
 
 typedef struct HVFState HVFState;
diff --git a/target/arm/hvf/hvf.c b/target/arm/hvf/hvf.c
index a028c99e24..09f41094e5 100644
--- a/target/arm/hvf/hvf.c
+++ b/target/arm/hvf/hvf.c
@@ -27,6 +27,7 @@
 #include "system/memory.h"
 #include "hw/core/boards.h"
 #include "hw/core/irq.h"
+#include "hw/arm/virt.h"
 #include "qemu/main-loop.h"
 #include "system/cpus.h"
 #include "arm-powerctl.h"
@@ -1103,6 +1104,10 @@ static bool hvf_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
                      (1ULL << ARM_FEATURE_PMU) |
                      (1ULL << ARM_FEATURE_GENERIC_TIMER);
 
+    if (hvf_nested_virt_enabled()) {
+        ahcf->features |= 1ULL << ARM_FEATURE_EL2;
+    }
+
     for (i = 0; i < ARRAY_SIZE(regs); i++) {
         r |= hv_vcpu_config_get_feature_reg(config, regs[i].reg,
                                             &host_isar.idregs[regs[i].index]);
@@ -1218,6 +1223,19 @@ void hvf_arch_vcpu_destroy(CPUState *cpu)
     assert_hvf_ok(ret);
 }
 
+static bool hvf_arm_el2_supported(void)
+{
+    bool is_nested_virt_supported;
+    if (__builtin_available(macOS 15.0, *)) {
+        hv_return_t ret = hv_vm_config_get_el2_supported(&is_nested_virt_supported);
+        assert_hvf_ok(ret);
+    } else {
+        return false;
+    }
+    return is_nested_virt_supported;
+}
+
+
 hv_return_t hvf_arch_vm_create(MachineState *ms, uint32_t pa_range)
 {
     hv_return_t ret;
@@ -1229,6 +1247,20 @@ hv_return_t hvf_arch_vm_create(MachineState *ms, uint32_t pa_range)
     }
     chosen_ipa_bit_size = pa_range;
 
+    if (__builtin_available(macOS 15.0, *)) {
+        if (hvf_nested_virt_enabled()) {
+            if (!hvf_arm_el2_supported()) {
+                error_report("Nested virtualization not supported on this system.");
+                goto cleanup;
+            }
+            ret = hv_vm_config_set_el2_enabled(config, true);
+            if (ret != HV_SUCCESS) {
+                error_report("Failed to enable nested virtualization.");
+                goto cleanup;
+            }
+        }
+    }
+
     ret = hv_vm_create(config);
     if (hvf_irqchip_in_kernel()) {
         if (__builtin_available(macOS 15.0, *)) {
@@ -1420,6 +1452,13 @@ static void hvf_psci_cpu_off(ARMCPU *arm_cpu)
     assert(ret == QEMU_ARM_POWERCTL_RET_SUCCESS);
 }
 
+static int hvf_psci_get_target_el(void)
+{
+    if (hvf_nested_virt_enabled()) {
+        return 2;
+    }
+    return 1;
+}
 /*
  * Handle a PSCI call.
  *
@@ -1441,7 +1480,6 @@ static bool hvf_handle_psci_call(CPUState *cpu, int *excp_ret)
     CPUState *target_cpu_state;
     ARMCPU *target_cpu;
     uint64_t entry;
-    int target_el = 1;
     int32_t ret = 0;
 
     trace_arm_psci_call(param[0], param[1], param[2], param[3],
@@ -1495,7 +1533,7 @@ static bool hvf_handle_psci_call(CPUState *cpu, int *excp_ret)
         entry = param[2];
         context_id = param[3];
         ret = arm_set_cpu_on(mpidr, entry, context_id,
-                             target_el, target_aarch64);
+                             hvf_psci_get_target_el(), target_aarch64);
         break;
     case QEMU_PSCI_0_1_FN_CPU_OFF:
     case QEMU_PSCI_0_2_FN_CPU_OFF:
-- 
2.43.0