[PATCH v7 17/24] whpx: arm64: clamp down IPA size

Mohamed Mediouni
2025-10-16T16:57:27Z

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>
---
hw/arm/virt.c | 32 ++++++++++++++++++++++++++
include/hw/boards.h | 1 +
target/arm/whpx/meson.build | 2 ++
target/arm/whpx/whpx-all.c | 45 +++++++++++++++++++++++++++++++++++++
target/arm/whpx/whpx-stub.c | 15 +++++++++++++
target/arm/whpx_arm.h | 16 +++++++++++++
6 files changed, 111 insertions(+)
create mode 100644 target/arm/whpx/whpx-stub.c
create mode 100644 target/arm/whpx_arm.h

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 1bebbc265d..b6b3e37f33 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -70,6 +70,7 @@
#include "hw/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"
@@ -3257,6 +3258,36 @@ 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. hvf_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);
@@ -3349,6 +3380,7 @@ 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;
diff --git a/include/hw/boards.h b/include/hw/boards.h
index 665b620121..3d01fb8cc9 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -276,6 +276,7 @@ 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;
diff --git a/target/arm/whpx/meson.build b/target/arm/whpx/meson.build
index 1de2ef0283..3df632c9d3 100644
--- a/target/arm/whpx/meson.build
+++ b/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'))
diff --git a/target/arm/whpx/whpx-all.c b/target/arm/whpx/whpx-all.c
index 7ef900a5ca..62fd6c230a 100644
--- a/target/arm/whpx/whpx-all.c
+++ b/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"

@@ -660,6 +661,40 @@ 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;
@@ -738,6 +773,7 @@ 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;

error:
@@ -760,6 +796,8 @@ int whpx_accel_init(AccelState *as, MachineState *ms)
UINT32 whpx_cap_size;
WHV_PARTITION_PROPERTY prop;
WHV_CAPABILITY_FEATURES features = {0};
+ MachineClass *mc = MACHINE_GET_CLASS(ms);
+ int pa_range = 0;

whpx = &whpx_global;
/* on arm64 Windows Hypervisor Platform, vGICv3 always used */
@@ -770,6 +808,13 @@ 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(
diff --git a/target/arm/whpx/whpx-stub.c b/target/arm/whpx/whpx-stub.c
new file mode 100644
index 0000000000..32e434a5f6
--- /dev/null
+++ b/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();
+}
diff --git a/target/arm/whpx_arm.h b/target/arm/whpx_arm.h
new file mode 100644
index 0000000000..de7406b66f
--- /dev/null
+++ b/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
--
2.50.1 (Apple Git-155)