whpx: arm64: clamp down IPA size

Code taken from HVF and adapted for WHPX use. Note that WHPX doesn't
have a default vs maximum IPA distinction.

Signed-off-by: Mohamed Mediouni <mohamed@unpredictable.fr>

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/arm/virt.c

@@ -72,6 +72,7 @@
 #include "hw/core/irq.h"
 #include "kvm_arm.h"
 #include "hvf_arm.h"
+#include "whpx_arm.h"
 #include "hw/firmware/smbios.h"
 #include "qapi/visitor.h"
 #include "qapi/qapi-visit-common.h"
@@ -3360,6 +3361,36 @@ static int virt_kvm_type(MachineState *ms, const char *type_str)
     return fixed_ipa ? 0 : requested_pa_size;
 }
 
+static int virt_whpx_get_physical_address_range(MachineState *ms)
+{
+    VirtMachineState *vms = VIRT_MACHINE(ms);
+
+    int max_ipa_size = whpx_arm_get_ipa_bit_size();
+
+    /* We freeze the memory map to compute the highest gpa */
+    virt_set_memmap(vms, max_ipa_size);
+
+    int requested_ipa_size = 64 - clz64(vms->highest_gpa);
+
+    /*
+     * If we're <= the default IPA size just use the default.
+     * If we're above the default but below the maximum, round up to
+     * the maximum. whpx_arm_get_max_ipa_bit_size() conveniently only
+     * returns values that are valid ARM PARange values.
+     */
+    if (requested_ipa_size <= max_ipa_size) {
+        requested_ipa_size = max_ipa_size;
+    } else {
+        error_report("-m and ,maxmem option values "
+                     "require an IPA range (%d bits) larger than "
+                     "the one supported by the host (%d bits)",
+                     requested_ipa_size, max_ipa_size);
+        return -1;
+    }
+
+    return requested_ipa_size;
+}
+
 static int virt_hvf_get_physical_address_range(MachineState *ms)
 {
     VirtMachineState *vms = VIRT_MACHINE(ms);
@@ -3459,6 +3490,7 @@ static void virt_machine_class_init(ObjectClass *oc, const void *data)
     mc->get_default_cpu_node_id = virt_get_default_cpu_node_id;
     mc->kvm_type = virt_kvm_type;
     mc->hvf_get_physical_address_range = virt_hvf_get_physical_address_range;
+    mc->whpx_get_physical_address_range = virt_whpx_get_physical_address_range;
     assert(!mc->get_hotplug_handler);
     mc->get_hotplug_handler = virt_machine_get_hotplug_handler;
     hc->pre_plug = virt_machine_device_pre_plug_cb;

include/hw/core/boards.h

@@ -278,6 +278,7 @@ struct MachineClass {
     void (*wakeup)(MachineState *state);
     int (*kvm_type)(MachineState *machine, const char *arg);
     int (*hvf_get_physical_address_range)(MachineState *machine);
+    int (*whpx_get_physical_address_range)(MachineState *machine);
 
     BlockInterfaceType block_default_type;
     int units_per_default_bus;

target/arm/whpx/meson.build

@@ -1,3 +1,5 @@
 arm_system_ss.add(when: 'CONFIG_WHPX', if_true: files(
   'whpx-all.c',
 ))
+
+arm_common_system_ss.add(when: 'CONFIG_WHPX', if_false: files('whpx-stub.c'))

target/arm/whpx/whpx-all.c

@@ -35,6 +35,7 @@
 #include "system/whpx-accel-ops.h"
 #include "system/whpx-all.h"
 #include "system/whpx-common.h"
+#include "whpx_arm.h"
 #include "hw/arm/bsa.h"
 #include "arm-powerctl.h"
 
@@ -633,6 +634,40 @@ static void whpx_cpu_update_state(void *opaque, bool running, RunState state)
 {
 }
 
+uint32_t whpx_arm_get_ipa_bit_size(void)
+{
+    WHV_CAPABILITY whpx_cap;
+    UINT32 whpx_cap_size;
+    HRESULT hr;
+    hr = whp_dispatch.WHvGetCapability(
+        WHvCapabilityCodePhysicalAddressWidth, &whpx_cap,
+        sizeof(whpx_cap), &whpx_cap_size);
+    if (FAILED(hr)) {
+        error_report("WHPX: failed to get supported "
+             "physical address width, hr=%08lx", hr);
+    }
+
+    /*
+     * We clamp any IPA size we want to back the VM with to a valid PARange
+     * value so the guest doesn't try and map memory outside of the valid range.
+     * This logic just clamps the passed in IPA bit size to the first valid
+     * PARange value <= to it.
+     */
+    return round_down_to_parange_bit_size(whpx_cap.PhysicalAddressWidth);
+}
+
+static void clamp_id_aa64mmfr0_parange_to_ipa_size(ARMISARegisters *isar)
+{
+    uint32_t ipa_size = whpx_arm_get_ipa_bit_size();
+    uint64_t id_aa64mmfr0;
+
+    /* Clamp down the PARange to the IPA size the kernel supports. */
+    uint8_t index = round_down_to_parange_index(ipa_size);
+    id_aa64mmfr0 = GET_IDREG(isar, ID_AA64MMFR0);
+    id_aa64mmfr0 = (id_aa64mmfr0 & ~R_ID_AA64MMFR0_PARANGE_MASK) | index;
+    SET_IDREG(isar, ID_AA64MMFR0, id_aa64mmfr0);
+}
+
 int whpx_init_vcpu(CPUState *cpu)
 {
     HRESULT hr;
@@ -706,6 +741,7 @@ int whpx_init_vcpu(CPUState *cpu)
     val.Reg64 = deposit64(arm_cpu->mp_affinity, 31, 1, 1 /* RES1 */);
     whpx_set_reg(cpu, WHvArm64RegisterMpidrEl1, val);
 
+    clamp_id_aa64mmfr0_parange_to_ipa_size(&arm_cpu->isar);
     return 0;
 }
 
@@ -722,6 +758,8 @@ int whpx_accel_init(AccelState *as, MachineState *ms)
     UINT32 whpx_cap_size;
     WHV_PARTITION_PROPERTY prop;
     WHV_CAPABILITY_FEATURES features;
+    MachineClass *mc = MACHINE_GET_CLASS(ms);
+    int pa_range = 0;
 
     whpx = &whpx_global;
     /* on arm64 Windows Hypervisor Platform, vGICv3 always used */
@@ -732,6 +770,13 @@ int whpx_accel_init(AccelState *as, MachineState *ms)
         goto error;
     }
 
+    if (mc->whpx_get_physical_address_range) {
+        pa_range = mc->whpx_get_physical_address_range(ms);
+        if (pa_range < 0) {
+            return -EINVAL;
+        }
+    }
+
     whpx->mem_quota = ms->ram_size;
 
     hr = whp_dispatch.WHvGetCapability(

target/arm/whpx/whpx-stub.c

@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * WHPX stubs for ARM
+ *
+ *  Copyright (c) 2025 Mohamed Mediouni
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "whpx_arm.h"
+
+uint32_t whpx_arm_get_ipa_bit_size(void)
+{
+    g_assert_not_reached();
+}

target/arm/whpx_arm.h

@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * WHPX support -- ARM specifics
+ *
+ * Copyright (c) 2025 Mohamed Mediouni
+ *
+ */
+
+#ifndef QEMU_WHPX_ARM_H
+#define QEMU_WHPX_ARM_H
+
+#include "target/arm/cpu-qom.h"
+
+uint32_t whpx_arm_get_ipa_bit_size(void);
+
+#endif