* [PATCH v2 0/2] arm: add kvm-psci-version vcpu property
@ 2025-10-30 16:59 Sebastian Ott
2025-10-30 16:59 ` [PATCH v2 1/2] target/arm/kvm: add constants for new PSCI versions Sebastian Ott
2025-10-30 16:59 ` [PATCH v2 2/2] target/arm/kvm: add kvm-psci-version vcpu property Sebastian Ott
0 siblings, 2 replies; 6+ messages in thread
From: Sebastian Ott @ 2025-10-30 16:59 UTC (permalink / raw)
To: Peter Maydell, Paolo Bonzini, Eric Auger
Cc: qemu-arm, qemu-devel, kvm, kvmarm, 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 V1 [1]:
* incorporated feedback from Peter and Eric
[1] https://lore.kernel.org/kvmarm/20250911144923.24259-1-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 | 60 +++++++++++++++++++++++++++++++-
4 files changed, 72 insertions(+), 1 deletion(-)
--
2.42.0
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v2 1/2] target/arm/kvm: add constants for new PSCI versions
2025-10-30 16:59 [PATCH v2 0/2] arm: add kvm-psci-version vcpu property Sebastian Ott
@ 2025-10-30 16:59 ` Sebastian Ott
2025-11-11 17:50 ` Eric Auger
2025-10-30 16:59 ` [PATCH v2 2/2] target/arm/kvm: add kvm-psci-version vcpu property Sebastian Ott
1 sibling, 1 reply; 6+ messages in thread
From: Sebastian Ott @ 2025-10-30 16:59 UTC (permalink / raw)
To: Peter Maydell, Paolo Bonzini, Eric Auger
Cc: qemu-arm, qemu-devel, kvm, kvmarm, Sebastian Ott
Add constants for PSCI version 1_2 and 1_3.
Signed-off-by: Sebastian Ott <sebott@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
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH v2 2/2] target/arm/kvm: add kvm-psci-version vcpu property
2025-10-30 16:59 [PATCH v2 0/2] arm: add kvm-psci-version vcpu property Sebastian Ott
2025-10-30 16:59 ` [PATCH v2 1/2] target/arm/kvm: add constants for new PSCI versions Sebastian Ott
@ 2025-10-30 16:59 ` Sebastian Ott
2025-11-11 17:57 ` Eric Auger
1 sibling, 1 reply; 6+ messages in thread
From: Sebastian Ott @ 2025-10-30 16:59 UTC (permalink / raw)
To: Peter Maydell, Paolo Bonzini, Eric Auger
Cc: qemu-arm, qemu-devel, kvm, kvmarm, 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
Signed-off-by: Sebastian Ott <sebott@redhat.com>
---
docs/system/arm/cpu-features.rst | 5 +++
target/arm/cpu.h | 6 ++++
target/arm/kvm.c | 60 +++++++++++++++++++++++++++++++-
3 files changed, 70 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..c53b307b76 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->prop_psci_version)
+ return g_strdup(ver->str);
+ }
+
+ g_assert_not_reached();
+}
+
+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 +2008,8 @@ 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)) {
cpu->psci_version = QEMU_PSCI_VERSION_0_2;
cpu->kvm_init_features[0] |= 1 << KVM_ARM_VCPU_PSCI_0_2;
}
@@ -1998,6 +2048,14 @@ 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
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v2 1/2] target/arm/kvm: add constants for new PSCI versions
2025-10-30 16:59 ` [PATCH v2 1/2] target/arm/kvm: add constants for new PSCI versions Sebastian Ott
@ 2025-11-11 17:50 ` Eric Auger
0 siblings, 0 replies; 6+ messages in thread
From: Eric Auger @ 2025-11-11 17:50 UTC (permalink / raw)
To: Sebastian Ott, Peter Maydell, Paolo Bonzini
Cc: qemu-arm, qemu-devel, kvm, kvmarm
Hi Sebstian,
On 10/30/25 5:59 PM, Sebastian Ott wrote:
> 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>
Eric
> ---
> 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 */
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2 2/2] target/arm/kvm: add kvm-psci-version vcpu property
2025-10-30 16:59 ` [PATCH v2 2/2] target/arm/kvm: add kvm-psci-version vcpu property Sebastian Ott
@ 2025-11-11 17:57 ` Eric Auger
2025-11-12 17:20 ` Sebastian Ott
0 siblings, 1 reply; 6+ messages in thread
From: Eric Auger @ 2025-11-11 17:57 UTC (permalink / raw)
To: Sebastian Ott, Peter Maydell, Paolo Bonzini
Cc: qemu-arm, qemu-devel, kvm, kvmarm
On 10/30/25 5:59 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
>
> Signed-off-by: Sebastian Ott <sebott@redhat.com>
> ---
> docs/system/arm/cpu-features.rst | 5 +++
> target/arm/cpu.h | 6 ++++
> target/arm/kvm.c | 60 +++++++++++++++++++++++++++++++-
> 3 files changed, 70 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..c53b307b76 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->prop_psci_version)
I still have the same question/comment as on v1. In case the end user
does not override the psci version I think you want to return the
default value, retrieved from KVM through KVM_REG_ARM_PSCI_VERSION and
which populates cpu->psci_version. So to me you should use
cpu->psci_version instead
> + return g_strdup(ver->str);
> + }
> +
> + g_assert_not_reached();
> +}
> +
> +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 +2008,8 @@ 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 &&
I don't understand what this change stands for. Please document it
through both a comment and a commit msg explanation
Thanks
Eric
> + kvm_check_extension(cs->kvm_state, KVM_CAP_ARM_PSCI_0_2)) {
> cpu->psci_version = QEMU_PSCI_VERSION_0_2;
> cpu->kvm_init_features[0] |= 1 << KVM_ARM_VCPU_PSCI_0_2;
> }
> @@ -1998,6 +2048,14 @@ 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
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2 2/2] target/arm/kvm: add kvm-psci-version vcpu property
2025-11-11 17:57 ` Eric Auger
@ 2025-11-12 17:20 ` Sebastian Ott
0 siblings, 0 replies; 6+ messages in thread
From: Sebastian Ott @ 2025-11-12 17:20 UTC (permalink / raw)
To: Eric Auger
Cc: Peter Maydell, Paolo Bonzini, qemu-arm, qemu-devel, kvm, kvmarm
On Tue, 11 Nov 2025, Eric Auger wrote:
> On 10/30/25 5:59 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
>>
>> Signed-off-by: Sebastian Ott <sebott@redhat.com>
>> ---
[...]
>> +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->prop_psci_version)
> I still have the same question/comment as on v1. In case the end user
> does not override the psci version I think you want to return the
> default value, retrieved from KVM through KVM_REG_ARM_PSCI_VERSION and
> which populates cpu->psci_version. So to me you should use
> cpu->psci_version instead
Sry, I didn't get your question the first time and double checked that the
VM uses the default/most recent version when the property is not set.
I just found out how to actually call this function (via qom-get) and
you're right: the VM uses the correct version but we report something
different here - and in this version even trigger the assertion. Ouch.
[...]
>> @@ -1959,7 +2008,8 @@ 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 &&
> I don't understand what this change stands for. Please document it
> through both a comment and a commit msg explanation
The explanation is in the cover letter - I'll move it to this patch.
Thanks,
Sebastian
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2025-11-12 17:23 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
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2025-10-30 16:59 [PATCH v2 0/2] arm: add kvm-psci-version vcpu property Sebastian Ott
2025-10-30 16:59 ` [PATCH v2 1/2] target/arm/kvm: add constants for new PSCI versions Sebastian Ott
2025-11-11 17:50 ` Eric Auger
2025-10-30 16:59 ` [PATCH v2 2/2] target/arm/kvm: add kvm-psci-version vcpu property Sebastian Ott
2025-11-11 17:57 ` Eric Auger
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