Commit a99e32dbd4 for qemu.org
commit a99e32dbd4a11fdf168438ded961a5fb70a37503
Author: Sebastian Ott <sebott@redhat.com>
Date: Thu Feb 26 11:27:18 2026 +0000
target/arm/kvm: add kvm-psci-version vcpu property
Provide a kvm specific vcpu property to override the default
(as of kernel v6.13 that would be PSCI v1.3) PSCI version emulated
by kvm. Current valid values are: 0.1, 0.2, 1.0, 1.1, 1.2, and 1.3
Note: in order to support PSCI v0.1 we need to drop vcpu
initialization with KVM_CAP_ARM_PSCI_0_2 in that case.
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Sebastian Ott <sebott@redhat.com>
Message-id: 20260220115656.4831-2-sebott@redhat.com
[PMM: adjust sscanf to not permit negative numbers]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/docs/system/arm/cpu-features.rst b/docs/system/arm/cpu-features.rst
index 3db1f19401..ce19ae6a04 100644
--- a/docs/system/arm/cpu-features.rst
+++ b/docs/system/arm/cpu-features.rst
@@ -204,6 +204,17 @@ the list of KVM VCPU features and their descriptions.
the guest scheduler behavior and/or be exposed to the guest
userspace.
+``kvm-psci-version``
+ Set the Power State Coordination Interface (PSCI) firmware ABI version
+ that KVM provides to the guest. By default KVM will use the newest
+ version that it knows about (which is PSCI v1.3 in Linux v6.13).
+
+ You only need to set this if you want to be able to migrate this
+ VM to a host machine running an older kernel that does not
+ recognize the PSCI version that this host's kernel defaults to.
+
+ Current valid values are: 0.1, 0.2, 1.0, 1.1, 1.2, and 1.3.
+
TCG VCPU Features
=================
diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index 10f8280eef..60f391651d 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -1144,7 +1144,13 @@ static void arm_cpu_initfn(Object *obj)
* picky DTB consumer will also provide a helpful error message.
*/
cpu->dtb_compatible = "qemu,unknown";
- cpu->psci_version = QEMU_PSCI_VERSION_0_1; /* By default assume PSCI v0.1 */
+ if (!kvm_enabled()) {
+ /* By default KVM will use the newest PSCI version that it knows about.
+ * This can be changed using the kvm-psci-version property.
+ * For others assume PSCI v0.1 by default.
+ */
+ cpu->psci_version = QEMU_PSCI_VERSION_0_1;
+ }
cpu->kvm_target = QEMU_KVM_ARM_TARGET_NONE;
if (tcg_enabled() || hvf_enabled()) {
diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index ded582e0da..c46ee9620b 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -485,6 +485,28 @@ static void kvm_steal_time_set(Object *obj, bool value, Error **errp)
ARM_CPU(obj)->kvm_steal_time = value ? ON_OFF_AUTO_ON : ON_OFF_AUTO_OFF;
}
+static char *kvm_get_psci_version(Object *obj, Error **errp)
+{
+ ARMCPU *cpu = ARM_CPU(obj);
+
+ return g_strdup_printf("%d.%d",
+ (int) PSCI_VERSION_MAJOR(cpu->psci_version),
+ (int) PSCI_VERSION_MINOR(cpu->psci_version));
+}
+
+static void kvm_set_psci_version(Object *obj, const char *value, Error **errp)
+{
+ ARMCPU *cpu = ARM_CPU(obj);
+ uint16_t maj, min;
+
+ if (sscanf(value, "%hu.%hu", &maj, &min) != 2) {
+ error_setg(errp, "Invalid PSCI version.");
+ return;
+ }
+
+ cpu->psci_version = PSCI_VERSION(maj, min);
+}
+
/* KVM VCPU properties should be prefixed with "kvm-". */
void kvm_arm_add_vcpu_properties(ARMCPU *cpu)
{
@@ -506,6 +528,12 @@ void kvm_arm_add_vcpu_properties(ARMCPU *cpu)
kvm_steal_time_set);
object_property_set_description(obj, "kvm-steal-time",
"Set off to disable KVM steal time.");
+
+ object_property_add_str(obj, "kvm-psci-version", kvm_get_psci_version,
+ kvm_set_psci_version);
+ object_property_set_description(obj, "kvm-psci-version",
+ "Set PSCI version. "
+ "Valid values are 0.1, 0.2, 1.0, 1.1, 1.2, 1.3");
}
bool kvm_arm_pmu_supported(void)
@@ -1976,8 +2004,12 @@ int kvm_arch_init_vcpu(CPUState *cs)
if (cs->start_powered_off) {
cpu->kvm_init_features[0] |= 1 << KVM_ARM_VCPU_POWER_OFF;
}
- if (kvm_check_extension(cs->kvm_state, KVM_CAP_ARM_PSCI_0_2)) {
- cpu->psci_version = QEMU_PSCI_VERSION_0_2;
+ if (cpu->psci_version != QEMU_PSCI_VERSION_0_1 &&
+ kvm_check_extension(cs->kvm_state, KVM_CAP_ARM_PSCI_0_2)) {
+ /*
+ * Versions >= v0.2 are backward compatible with v0.2
+ * omit the feature flag for v0.1 .
+ */
cpu->kvm_init_features[0] |= 1 << KVM_ARM_VCPU_PSCI_0_2;
}
if (!arm_feature(env, ARM_FEATURE_AARCH64)) {
@@ -2015,6 +2047,18 @@ int kvm_arch_init_vcpu(CPUState *cs)
}
}
+ if (cpu->psci_version) {
+ psciver = cpu->psci_version;
+ ret = kvm_set_one_reg(cs, KVM_REG_ARM_PSCI_VERSION, &psciver);
+ if (ret) {
+ error_report("KVM in this kernel does not support PSCI version %d.%d",
+ (int) PSCI_VERSION_MAJOR(psciver),
+ (int) PSCI_VERSION_MINOR(psciver));
+ error_printf("Consider setting the kvm-psci-version property on the "
+ "migration source.\n");
+ return ret;
+ }
+ }
/*
* KVM reports the exact PSCI version it is implementing via a
* special sysreg. If it is present, use its contents to determine