[PATCH v3 0/2] arm: add kvm-psci-version vcpu property

[PATCH v3 0/2] arm: add kvm-psci-version vcpu property

[Sebastian Ott]

This series adds a vcpu knob to request a specific PSCI version
from KVM via the KVM_REG_ARM_PSCI_VERSION FW register.

The use case for this is to support migration between host kernels
that differ in their default (a.k.a. most recent) PSCI version.

Note: in order to support PSCI v0.1 we need to drop vcpu
initialization with KVM_CAP_ARM_PSCI_0_2 in that case.
Alternatively we could limit support to versions >=0.2 .

Changes since V2 [2]:
* fix kvm_get_psci_version() when the prop is not specified - thanks Eric!
* removed the assertion in kvm_get_psci_version() so that this also works
  with a future kernel/psci version
* added R-B
Changes since V1 [1]:
* incorporated feedback from Peter and Eric

[1] https://lore.kernel.org/kvmarm/20250911144923.24259-1-sebott@redhat.com/
[2] https://lore.kernel.org/kvmarm/20251030165905.73295-1-sebott@redhat.com/


Sebastian Ott (2):
  target/arm/kvm: add constants for new PSCI versions
  target/arm/kvm: add kvm-psci-version vcpu property

 docs/system/arm/cpu-features.rst |  5 +++
 target/arm/cpu.h                 |  6 +++
 target/arm/kvm-consts.h          |  2 +
 target/arm/kvm.c                 | 64 +++++++++++++++++++++++++++++++-
 4 files changed, 76 insertions(+), 1 deletion(-)

-- 
2.42.0

[PATCH v3 1/2] target/arm/kvm: add constants for new PSCI versions

[Sebastian Ott]

Add constants for PSCI version 1_2 and 1_3.

Signed-off-by: Sebastian Ott <sebott@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
---
 target/arm/kvm-consts.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/target/arm/kvm-consts.h b/target/arm/kvm-consts.h
index 54ae5da7ce..9fba3e886d 100644
--- a/target/arm/kvm-consts.h
+++ b/target/arm/kvm-consts.h
@@ -97,6 +97,8 @@ MISMATCH_CHECK(QEMU_PSCI_1_0_FN_PSCI_FEATURES, PSCI_1_0_FN_PSCI_FEATURES);
 #define QEMU_PSCI_VERSION_0_2                     0x00002
 #define QEMU_PSCI_VERSION_1_0                     0x10000
 #define QEMU_PSCI_VERSION_1_1                     0x10001
+#define QEMU_PSCI_VERSION_1_2                     0x10002
+#define QEMU_PSCI_VERSION_1_3                     0x10003
 
 MISMATCH_CHECK(QEMU_PSCI_0_2_RET_TOS_MIGRATION_NOT_REQUIRED, PSCI_0_2_TOS_MP);
 /* We don't bother to check every possible version value */
-- 
2.42.0

[PATCH v3 2/2] target/arm/kvm: add kvm-psci-version vcpu property

[Sebastian Ott]

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.

Signed-off-by: Sebastian Ott <sebott@redhat.com>
---
 docs/system/arm/cpu-features.rst |  5 +++
 target/arm/cpu.h                 |  6 +++
 target/arm/kvm.c                 | 64 +++++++++++++++++++++++++++++++-
 3 files changed, 74 insertions(+), 1 deletion(-)

diff --git a/docs/system/arm/cpu-features.rst b/docs/system/arm/cpu-features.rst
index 37d5dfd15b..1d32ce0fee 100644
--- a/docs/system/arm/cpu-features.rst
+++ b/docs/system/arm/cpu-features.rst
@@ -204,6 +204,11 @@ the list of KVM VCPU features and their descriptions.
   the guest scheduler behavior and/or be exposed to the guest
   userspace.
 
+``kvm-psci-version``
+  Override the default (as of kernel v6.13 that would be PSCI v1.3)
+  PSCI version emulated by the kernel. 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.h b/target/arm/cpu.h
index 39f2b2e54d..c2032070b7 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -981,6 +981,12 @@ struct ArchCPU {
      */
     uint32_t psci_version;
 
+    /*
+     * Intermediate value used during property parsing.
+     * Once finalized, the value should be read from psci_version.
+     */
+    uint32_t prop_psci_version;
+
     /* Current power state, access guarded by BQL */
     ARMPSCIState power_state;
 
diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index 0d57081e69..e91b1abfb8 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -484,6 +484,49 @@ 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;
 }
 
+struct psci_version {
+    uint32_t number;
+    const char *str;
+};
+
+static const struct psci_version psci_versions[] = {
+    { QEMU_PSCI_VERSION_0_1, "0.1" },
+    { QEMU_PSCI_VERSION_0_2, "0.2" },
+    { QEMU_PSCI_VERSION_1_0, "1.0" },
+    { QEMU_PSCI_VERSION_1_1, "1.1" },
+    { QEMU_PSCI_VERSION_1_2, "1.2" },
+    { QEMU_PSCI_VERSION_1_3, "1.3" },
+    { -1, NULL },
+};
+
+static char *kvm_get_psci_version(Object *obj, Error **errp)
+{
+    ARMCPU *cpu = ARM_CPU(obj);
+    const struct psci_version *ver;
+
+    for (ver = psci_versions; ver->number != -1; ver++) {
+        if (ver->number == cpu->psci_version)
+            return g_strdup(ver->str);
+    }
+
+    return g_strdup_printf("Unknown PSCI-version: %x", cpu->psci_version);
+}
+
+static void kvm_set_psci_version(Object *obj, const char *value, Error **errp)
+{
+    ARMCPU *cpu = ARM_CPU(obj);
+    const struct psci_version *ver;
+
+    for (ver = psci_versions; ver->number != -1; ver++) {
+        if (!strcmp(value, ver->str)) {
+            cpu->prop_psci_version = ver->number;
+            return;
+        }
+    }
+
+    error_setg(errp, "Invalid PSCI-version value");
+}
+
 /* KVM VCPU properties should be prefixed with "kvm-". */
 void kvm_arm_add_vcpu_properties(ARMCPU *cpu)
 {
@@ -505,6 +548,12 @@ 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)
@@ -1959,7 +2008,12 @@ 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)) {
+    if (cpu->prop_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->psci_version = QEMU_PSCI_VERSION_0_2;
         cpu->kvm_init_features[0] |= 1 << KVM_ARM_VCPU_PSCI_0_2;
     }
@@ -1998,6 +2052,14 @@ int kvm_arch_init_vcpu(CPUState *cs)
         }
     }
 
+    if (cpu->prop_psci_version) {
+        psciver = cpu->prop_psci_version;
+        ret = kvm_set_one_reg(cs, KVM_REG_ARM_PSCI_VERSION, &psciver);
+        if (ret) {
+            error_report("PSCI version %"PRIx64" is not supported by KVM", psciver);
+            return ret;
+        }
+    }
     /*
      * KVM reports the exact PSCI version it is implementing via a
      * special sysreg. If it is present, use its contents to determine
-- 
2.42.0

Re: [PATCH v3 2/2] target/arm/kvm: add kvm-psci-version vcpu property

[Philippe Mathieu-Daudé]

Hi Sebastian,

On 12/11/25 19:13, Sebastian Ott wrote:
> 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.
> 
> Signed-off-by: Sebastian Ott <sebott@redhat.com>
> ---
>   docs/system/arm/cpu-features.rst |  5 +++
>   target/arm/cpu.h                 |  6 +++
>   target/arm/kvm.c                 | 64 +++++++++++++++++++++++++++++++-
>   3 files changed, 74 insertions(+), 1 deletion(-)


> diff --git a/target/arm/kvm.c b/target/arm/kvm.c
> index 0d57081e69..e91b1abfb8 100644
> --- a/target/arm/kvm.c
> +++ b/target/arm/kvm.c
> @@ -484,6 +484,49 @@ 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;
>   }
>   
> +struct psci_version {
> +    uint32_t number;
> +    const char *str;
> +};
> +
> +static const struct psci_version psci_versions[] = {
> +    { QEMU_PSCI_VERSION_0_1, "0.1" },
> +    { QEMU_PSCI_VERSION_0_2, "0.2" },
> +    { QEMU_PSCI_VERSION_1_0, "1.0" },
> +    { QEMU_PSCI_VERSION_1_1, "1.1" },
> +    { QEMU_PSCI_VERSION_1_2, "1.2" },
> +    { QEMU_PSCI_VERSION_1_3, "1.3" },
> +    { -1, NULL },
> +};


> @@ -505,6 +548,12 @@ 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");

Could we enumerate from psci_versions[] here?

>   }
Thanks,

Phil.

Re: [PATCH v3 2/2] target/arm/kvm: add kvm-psci-version vcpu property

[Sebastian Ott]

[-- Attachment #1: Type: text/plain, Size: 2863 bytes --]

Hi Philippe,

On Wed, 12 Nov 2025, Philippe Mathieu-Daudé wrote:
> On 12/11/25 19:13, Sebastian Ott wrote:
>>  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.
>>
>>  Signed-off-by: Sebastian Ott <sebott@redhat.com>
>>  ---
>>    docs/system/arm/cpu-features.rst |  5 +++
>>    target/arm/cpu.h                 |  6 +++
>>    target/arm/kvm.c                 | 64 +++++++++++++++++++++++++++++++-
>>    3 files changed, 74 insertions(+), 1 deletion(-)
>
>
>>  diff --git a/target/arm/kvm.c b/target/arm/kvm.c
>>  index 0d57081e69..e91b1abfb8 100644
>>  --- a/target/arm/kvm.c
>>  +++ b/target/arm/kvm.c
>>  @@ -484,6 +484,49 @@ 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;
>>    }
>>
>>  +struct psci_version {
>>  +    uint32_t number;
>>  +    const char *str;
>>  +};
>>  +
>>  +static const struct psci_version psci_versions[] = {
>>  +    { QEMU_PSCI_VERSION_0_1, "0.1" },
>>  +    { QEMU_PSCI_VERSION_0_2, "0.2" },
>>  +    { QEMU_PSCI_VERSION_1_0, "1.0" },
>>  +    { QEMU_PSCI_VERSION_1_1, "1.1" },
>>  +    { QEMU_PSCI_VERSION_1_2, "1.2" },
>>  +    { QEMU_PSCI_VERSION_1_3, "1.3" },
>>  +    { -1, NULL },
>>  +};
>
>
>>  @@ -505,6 +548,12 @@ 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");
>
> Could we enumerate from psci_versions[] here?
>

Hm, we'd need to concatenate these. Either manually:
"Valid values are " psci_versions[0].str ", " psci_versions[1].str ", " ... 
which is not pretty and still needs to be touched for a new version.

Or by a helper function that puts these in a new array and uses smth like
g_strjoinv(", ", array);
But that's quite a bit of extra code that needs to be maintained without
much gain.

Or we shy away from the issue and rephrase that to:
"Valid values include 1.0, 1.1, 1.2, 1.3"

Since the intended use case is via machine types and I don't expect a
lot of users setting the psci version manually - I vote for option 3.

Opinions?

Sebastian

Re: [PATCH v3 2/2] target/arm/kvm: add kvm-psci-version vcpu property

[Eric Auger]

On 11/13/25 1:05 PM, Sebastian Ott wrote:
> Hi Philippe,
>
> On Wed, 12 Nov 2025, Philippe Mathieu-Daudé wrote:
>> On 12/11/25 19:13, Sebastian Ott wrote:
>>>  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.
>>>
>>>  Signed-off-by: Sebastian Ott <sebott@redhat.com>
>>>  ---
>>>    docs/system/arm/cpu-features.rst |  5 +++
>>>    target/arm/cpu.h                 |  6 +++
>>>    target/arm/kvm.c                 | 64
>>> +++++++++++++++++++++++++++++++-
>>>    3 files changed, 74 insertions(+), 1 deletion(-)
>>
>>
>>>  diff --git a/target/arm/kvm.c b/target/arm/kvm.c
>>>  index 0d57081e69..e91b1abfb8 100644
>>>  --- a/target/arm/kvm.c
>>>  +++ b/target/arm/kvm.c
>>>  @@ -484,6 +484,49 @@ 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;
>>>    }
>>>
>>>  +struct psci_version {
>>>  +    uint32_t number;
>>>  +    const char *str;
>>>  +};
>>>  +
>>>  +static const struct psci_version psci_versions[] = {
>>>  +    { QEMU_PSCI_VERSION_0_1, "0.1" },
>>>  +    { QEMU_PSCI_VERSION_0_2, "0.2" },
>>>  +    { QEMU_PSCI_VERSION_1_0, "1.0" },
>>>  +    { QEMU_PSCI_VERSION_1_1, "1.1" },
>>>  +    { QEMU_PSCI_VERSION_1_2, "1.2" },
>>>  +    { QEMU_PSCI_VERSION_1_3, "1.3" },
>>>  +    { -1, NULL },
>>>  +};
>>
>>
>>>  @@ -505,6 +548,12 @@ 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");
>>
>> Could we enumerate from psci_versions[] here?
>>
>
> Hm, we'd need to concatenate these. Either manually:
> "Valid values are " psci_versions[0].str ", " psci_versions[1].str ",
> " ... which is not pretty and still needs to be touched for a new
> version.
>
> Or by a helper function that puts these in a new array and uses smth like
> g_strjoinv(", ", array);
> But that's quite a bit of extra code that needs to be maintained without
> much gain.
>
> Or we shy away from the issue and rephrase that to:
> "Valid values include 1.0, 1.1, 1.2, 1.3" 
Personally I would vote for keeping it as is (by the way why did you
moit 0.1 and 0.2 above?)

Eric
>
> Since the intended use case is via machine types and I don't expect a
> lot of users setting the psci version manually - I vote for option 3.
>
> Opinions?
>
> Sebastian

Re: [PATCH v3 2/2] target/arm/kvm: add kvm-psci-version vcpu property

[Eric Auger]

Hi Sebastian,

On 11/12/25 7:13 PM, Sebastian Ott wrote:
> 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.
>
> Signed-off-by: Sebastian Ott <sebott@redhat.com>
> ---
>  docs/system/arm/cpu-features.rst |  5 +++
>  target/arm/cpu.h                 |  6 +++
>  target/arm/kvm.c                 | 64 +++++++++++++++++++++++++++++++-
>  3 files changed, 74 insertions(+), 1 deletion(-)
>
> diff --git a/docs/system/arm/cpu-features.rst b/docs/system/arm/cpu-features.rst
> index 37d5dfd15b..1d32ce0fee 100644
> --- a/docs/system/arm/cpu-features.rst
> +++ b/docs/system/arm/cpu-features.rst
> @@ -204,6 +204,11 @@ the list of KVM VCPU features and their descriptions.
>    the guest scheduler behavior and/or be exposed to the guest
>    userspace.
>  
> +``kvm-psci-version``
> +  Override the default (as of kernel v6.13 that would be PSCI v1.3)
> +  PSCI version emulated by the kernel. 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.h b/target/arm/cpu.h
> index 39f2b2e54d..c2032070b7 100644
> --- a/target/arm/cpu.h
> +++ b/target/arm/cpu.h
> @@ -981,6 +981,12 @@ struct ArchCPU {
>       */
>      uint32_t psci_version;
>  
> +    /*
> +     * Intermediate value used during property parsing.
> +     * Once finalized, the value should be read from psci_version.
> +     */
> +    uint32_t prop_psci_version;
nit: as it is a kvm only thingy, could could rename it with kvm_ prefix
and move this along with the other kvm_* elements
> +
>      /* Current power state, access guarded by BQL */
>      ARMPSCIState power_state;
>  
> diff --git a/target/arm/kvm.c b/target/arm/kvm.c
> index 0d57081e69..e91b1abfb8 100644
> --- a/target/arm/kvm.c
> +++ b/target/arm/kvm.c
> @@ -484,6 +484,49 @@ 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;
>  }
>  
> +struct psci_version {
> +    uint32_t number;
> +    const char *str;
> +};
> +
> +static const struct psci_version psci_versions[] = {
> +    { QEMU_PSCI_VERSION_0_1, "0.1" },
> +    { QEMU_PSCI_VERSION_0_2, "0.2" },
> +    { QEMU_PSCI_VERSION_1_0, "1.0" },
> +    { QEMU_PSCI_VERSION_1_1, "1.1" },
> +    { QEMU_PSCI_VERSION_1_2, "1.2" },
> +    { QEMU_PSCI_VERSION_1_3, "1.3" },
> +    { -1, NULL },
> +};
> +
> +static char *kvm_get_psci_version(Object *obj, Error **errp)
> +{
> +    ARMCPU *cpu = ARM_CPU(obj);
> +    const struct psci_version *ver;
> +
> +    for (ver = psci_versions; ver->number != -1; ver++) {
> +        if (ver->number == cpu->psci_version)
> +            return g_strdup(ver->str);
> +    }
> +
> +    return g_strdup_printf("Unknown PSCI-version: %x", cpu->psci_version);
> +}
> +
> +static void kvm_set_psci_version(Object *obj, const char *value, Error **errp)
> +{
> +    ARMCPU *cpu = ARM_CPU(obj);
> +    const struct psci_version *ver;
> +
> +    for (ver = psci_versions; ver->number != -1; ver++) {
> +        if (!strcmp(value, ver->str)) {
> +            cpu->prop_psci_version = ver->number;
> +            return;
> +        }
> +    }
> +
> +    error_setg(errp, "Invalid PSCI-version value");
> +}
> +
>  /* KVM VCPU properties should be prefixed with "kvm-". */
>  void kvm_arm_add_vcpu_properties(ARMCPU *cpu)
>  {
> @@ -505,6 +548,12 @@ 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)
> @@ -1959,7 +2008,12 @@ 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)) {
> +    if (cpu->prop_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->psci_version = QEMU_PSCI_VERSION_0_2;
>          cpu->kvm_init_features[0] |= 1 << KVM_ARM_VCPU_PSCI_0_2;
>      }
> @@ -1998,6 +2052,14 @@ int kvm_arch_init_vcpu(CPUState *cs)
>          }
>      }
>  
> +    if (cpu->prop_psci_version) {
> +        psciver = cpu->prop_psci_version;
> +        ret = kvm_set_one_reg(cs, KVM_REG_ARM_PSCI_VERSION, &psciver);
> +        if (ret) {
> +            error_report("PSCI version %"PRIx64" is not supported by KVM", psciver);
> +            return ret;
> +        }
> +    }
>      /*
>       * KVM reports the exact PSCI version it is implementing via a
>       * special sysreg. If it is present, use its contents to determine
Besides it looks good to me.
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Eric

Re: [PATCH v3 2/2] target/arm/kvm: add kvm-psci-version vcpu property

[Philippe Mathieu-Daudé]

On 20/11/25 11:10, Eric Auger wrote:
> 
> 
> On 11/13/25 1:05 PM, Sebastian Ott wrote:
>> Hi Philippe,
>>
>> On Wed, 12 Nov 2025, Philippe Mathieu-Daudé wrote:
>>> On 12/11/25 19:13, Sebastian Ott wrote:
>>>>   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.
>>>>
>>>>   Signed-off-by: Sebastian Ott <sebott@redhat.com>
>>>>   ---
>>>>     docs/system/arm/cpu-features.rst |  5 +++
>>>>     target/arm/cpu.h                 |  6 +++
>>>>     target/arm/kvm.c                 | 64
>>>> +++++++++++++++++++++++++++++++-
>>>>     3 files changed, 74 insertions(+), 1 deletion(-)
>>>
>>>
>>>>   diff --git a/target/arm/kvm.c b/target/arm/kvm.c
>>>>   index 0d57081e69..e91b1abfb8 100644
>>>>   --- a/target/arm/kvm.c
>>>>   +++ b/target/arm/kvm.c
>>>>   @@ -484,6 +484,49 @@ 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;
>>>>     }
>>>>
>>>>   +struct psci_version {
>>>>   +    uint32_t number;
>>>>   +    const char *str;
>>>>   +};
>>>>   +
>>>>   +static const struct psci_version psci_versions[] = {
>>>>   +    { QEMU_PSCI_VERSION_0_1, "0.1" },
>>>>   +    { QEMU_PSCI_VERSION_0_2, "0.2" },
>>>>   +    { QEMU_PSCI_VERSION_1_0, "1.0" },
>>>>   +    { QEMU_PSCI_VERSION_1_1, "1.1" },
>>>>   +    { QEMU_PSCI_VERSION_1_2, "1.2" },
>>>>   +    { QEMU_PSCI_VERSION_1_3, "1.3" },
>>>>   +    { -1, NULL },
>>>>   +};
>>>
>>>
>>>>   @@ -505,6 +548,12 @@ 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");
>>>
>>> Could we enumerate from psci_versions[] here?
>>>
>>
>> Hm, we'd need to concatenate these. Either manually:
>> "Valid values are " psci_versions[0].str ", " psci_versions[1].str ",
>> " ... which is not pretty and still needs to be touched for a new
>> version.
>>
>> Or by a helper function that puts these in a new array and uses smth like
>> g_strjoinv(", ", array);
>> But that's quite a bit of extra code that needs to be maintained without
>> much gain.
>>
>> Or we shy away from the issue and rephrase that to:
>> "Valid values include 1.0, 1.1, 1.2, 1.3"
> Personally I would vote for keeping it as is

OK.

> (by the way why did you
> moit 0.1 and 0.2 above?)
> 
> Eric
>>
>> Since the intended use case is via machine types and I don't expect a
>> lot of users setting the psci version manually - I vote for option 3.
>>
>> Opinions?
>>
>> Sebastian
> 

Re: [PATCH v3 2/2] target/arm/kvm: add kvm-psci-version vcpu property

[Sebastian Ott]

[-- Attachment #1: Type: text/plain, Size: 3509 bytes --]

On Thu, 20 Nov 2025, Eric Auger wrote:
> On 11/13/25 1:05 PM, Sebastian Ott wrote:
>> Hi Philippe,
>>
>> On Wed, 12 Nov 2025, Philippe Mathieu-Daudé wrote:
>>> On 12/11/25 19:13, Sebastian Ott wrote:
>>>>  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.
>>>>
>>>>  Signed-off-by: Sebastian Ott <sebott@redhat.com>
>>>>  ---
>>>>    docs/system/arm/cpu-features.rst |  5 +++
>>>>    target/arm/cpu.h                 |  6 +++
>>>>    target/arm/kvm.c                 | 64
>>>> +++++++++++++++++++++++++++++++-
>>>>    3 files changed, 74 insertions(+), 1 deletion(-)
>>>
>>>
>>>>  diff --git a/target/arm/kvm.c b/target/arm/kvm.c
>>>>  index 0d57081e69..e91b1abfb8 100644
>>>>  --- a/target/arm/kvm.c
>>>>  +++ b/target/arm/kvm.c
>>>>  @@ -484,6 +484,49 @@ 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;
>>>>    }
>>>>
>>>>  +struct psci_version {
>>>>  +    uint32_t number;
>>>>  +    const char *str;
>>>>  +};
>>>>  +
>>>>  +static const struct psci_version psci_versions[] = {
>>>>  +    { QEMU_PSCI_VERSION_0_1, "0.1" },
>>>>  +    { QEMU_PSCI_VERSION_0_2, "0.2" },
>>>>  +    { QEMU_PSCI_VERSION_1_0, "1.0" },
>>>>  +    { QEMU_PSCI_VERSION_1_1, "1.1" },
>>>>  +    { QEMU_PSCI_VERSION_1_2, "1.2" },
>>>>  +    { QEMU_PSCI_VERSION_1_3, "1.3" },
>>>>  +    { -1, NULL },
>>>>  +};
>>>
>>>
>>>>  @@ -505,6 +548,12 @@ 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");
>>>
>>> Could we enumerate from psci_versions[] here?
>>>
>>
>> Hm, we'd need to concatenate these. Either manually:
>> "Valid values are " psci_versions[0].str ", " psci_versions[1].str ",
>> " ... which is not pretty and still needs to be touched for a new
>> version.
>>
>> Or by a helper function that puts these in a new array and uses smth like
>> g_strjoinv(", ", array);
>> But that's quite a bit of extra code that needs to be maintained without
>> much gain.
>>
>> Or we shy away from the issue and rephrase that to:
>> "Valid values include 1.0, 1.1, 1.2, 1.3" 
> Personally I would vote for keeping it as is

OK, thanks!

> (by the way why did you
> moit 0.1 and 0.2 above?)

Just to clarify that this is an incomplete list of possible values
that we don't have to change when a new psci version is introduced.

Sebastian