[RFC PATCH v7 14/28] KVM: arm64: Add SPE VCPU device attribute to initialize SPE
Lorenzo Stoakes (ARM)
ljs at kernel.org
Wed Oct 28 06:45:05 PDT 2026
On Thu, Sep 03, 2026 at 05:06:09PM +0100, Alexandru Elisei wrote:
> Add KVM_ARM_VCPU_SPE_CTRL(KVM_ARM_VCPU_SPE_INIT) VCPU ioctl to initialize
> SPE. Initialization must be done exactly once for each VCPU.
Again be good to have a little more in the commit message.
>
> [ Alexandru E: Split from "KVM: arm64: Add a new VCPU device control group
> for SPE" ]
>
> Signed-off-by: Sudeep Holla <sudeep.holla at arm.com>
> Signed-off-by: Alexandru Elisei <alexandru.elisei at arm.com>
> ---
> Documentation/virt/kvm/devices/vcpu.rst | 28 ++++++++++++++++++++---
> arch/arm64/include/asm/kvm_spe.h | 6 +++++
> arch/arm64/include/uapi/asm/kvm.h | 1 +
> arch/arm64/kvm/arm.c | 6 +++++
> arch/arm64/kvm/spe.c | 30 +++++++++++++++++++++++++
> 5 files changed, 68 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/virt/kvm/devices/vcpu.rst b/Documentation/virt/kvm/devices/vcpu.rst
> index d60dd1daa67f..e2eac48b9d28 100644
> --- a/Documentation/virt/kvm/devices/vcpu.rst
> +++ b/Documentation/virt/kvm/devices/vcpu.rst
> @@ -317,6 +317,7 @@ From the destination VMM process:
> Returns:
>
> ======= ==========================================================
> + -EBUSY SPE already initialized
> -EFAULT Error accessing the buffer management interrupt number
> -EINVAL Invalid interrupt number or not using an in-kernel irqchip
> -ENODEV KVM_ARM_VCPU_HAS_SPE VCPU feature not set
> @@ -338,15 +339,15 @@ vGIC implementation.
>
> :Returns:
Just highlighting again the very nitty point about consistency between
'Returns:' and ':Returns:' :P.
>
> - ======= =========================================================
> - -EBUSY Virtual machine has already run
> + ======= ===========================================================
> + -EBUSY Virtual machine has already run, or SPE already initialized
> -EFAULT Error accessing the SPE identifier
> -EINVAL A different SPE instance already assigned, or no physical
> CPUs found
> -ENXIO SPE not supported or not properly configured, or the SPE
> module not loaded
> -ENODEV KVM_ARM_VCPU_HAS_SPE VCPU feature not set
> - ======= =========================================================
> + ======= ===========================================================
>
> Required.
>
> @@ -361,3 +362,24 @@ responsible for making sure that the VCPU is run only on physical CPUs which
> share the specified SPE instance. If the VCPU has a PMU assigned, and there are
> no physical CPUs which share the same SPE and PMU instance, an error is
> returned.
> +
> +5.3 ATTRIBUTE: KVM_ARM_VCPU_SPE_INIT
> +-----------------------------------
This underline looks short?
> +
> +:Parameters: no additional parameter in kvm_device_attr.addr
> +
> +Returns:
> +
> + ======= ============================================
> + -EBUSY SPE already initialized for this VCPU
> + -ENXIO SPE not supported or not properly configured
> + ======= ============================================
> +
> +Required.
> +
> +Request initialization of the Statistical Profiling Extension for this VCPU.
> +Must be done last, after SPE has been fully configured for the VCPU, and after
> +the in-kernel irqchip has been initialized.
> +
> +KVM will refuse to run the VCPU and KVM_RUN will return an error if the SPE
> +feature has been set for the VCPU, but SPE hasn't been initialized.
> diff --git a/arch/arm64/include/asm/kvm_spe.h b/arch/arm64/include/asm/kvm_spe.h
> index b8afb419c851..a6999709b298 100644
> --- a/arch/arm64/include/asm/kvm_spe.h
> +++ b/arch/arm64/include/asm/kvm_spe.h
> @@ -18,6 +18,7 @@ struct kvm_spe {
>
> struct kvm_vcpu_spe {
> int irq_num; /* Buffer management interrupt number */
> + bool initialized; /* SPE initialized for the VCPU */
> };
>
> bool kvm_supports_spe(void);
> @@ -25,6 +26,7 @@ bool kvm_supports_spe(void);
> #define vcpu_has_spe(vcpu) \
> (vcpu_has_feature(vcpu, KVM_ARM_VCPU_SPE))
>
> +int kvm_spe_vcpu_first_run_init(struct kvm_vcpu *vcpu);
> void kvm_spe_destroy_vm(struct kvm *kvm);
>
> int kvm_spe_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr);
> @@ -46,6 +48,10 @@ static __always_inline bool kvm_supports_spe(void)
>
> #define vcpu_has_spe(vcpu) false
>
> +static inline int kvm_spe_vcpu_first_run_init(struct kvm_vcpu *vcpu)
> +{
> + return 0;
> +}
> static inline void kvm_spe_destroy_vm(struct kvm *kvm)
> {
> }
> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> index 8ffa3e89d38c..c695aae484d3 100644
> --- a/arch/arm64/include/uapi/asm/kvm.h
> +++ b/arch/arm64/include/uapi/asm/kvm.h
> @@ -449,6 +449,7 @@ enum {
> #define KVM_ARM_VCPU_SPE_CTRL 3
> #define KVM_ARM_VCPU_SPE_IRQ 0
> #define KVM_ARM_VCPU_SPE_ID 1
> +#define KVM_ARM_VCPU_SPE_INIT 2
>
> /* KVM_IRQ_LINE irq field index values */
> #define KVM_ARM_IRQ_VCPU2_SHIFT 28
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 132df44c3088..c9a026c61ce7 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -1026,6 +1026,12 @@ int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
> return ret;
> }
>
> + if (vcpu_has_spe(vcpu)) {
> + ret = kvm_spe_vcpu_first_run_init(vcpu);
> + if (ret)
> + return ret;
> + }
> +
> ret = vgic_v5_finalize_ppi_state(kvm);
> if (ret)
> return ret;
> diff --git a/arch/arm64/kvm/spe.c b/arch/arm64/kvm/spe.c
> index 87fcdbbcbd67..fa87d224c8af 100644
> --- a/arch/arm64/kvm/spe.c
> +++ b/arch/arm64/kvm/spe.c
> @@ -59,6 +59,16 @@ bool kvm_supports_spe(void)
> return !list_empty(&spe_pmus);
> }
>
> +int kvm_spe_vcpu_first_run_init(struct kvm_vcpu *vcpu)
This isn't initialising anything, I guess you plan to build it up over patches
but maybe worth mentioning that in the commit msg?
> +{
> + struct kvm_vcpu_spe *vcpu_spe = &vcpu->arch.vcpu_spe;
> +
> + if (!vcpu_spe->initialized)
> + return -EINVAL;
> +
> + return 0;
> +}
> +
> void kvm_spe_destroy_vm(struct kvm *kvm)
> {
> struct arm_spe_pmu *spe_pmu;
> @@ -147,12 +157,16 @@ int kvm_spe_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
> {
> struct kvm_vcpu_spe *vcpu_spe = &vcpu->arch.vcpu_spe;
> struct kvm *kvm = vcpu->kvm;
> + struct kvm_spe *kvm_spe = &kvm->arch.kvm_spe;
>
> lockdep_assert_held(&kvm->arch.config_lock);
>
> if (!vcpu_has_spe(vcpu))
> return -ENODEV;
>
> + if (vcpu_spe->initialized)
> + return -EBUSY;
> +
> switch (attr->attr) {
> case KVM_ARM_VCPU_SPE_IRQ: {
> int __user *uaddr = (int __user *)(long)attr->addr;
> @@ -182,6 +196,21 @@ int kvm_spe_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
>
> return kvm_spe_set_spe_id(vcpu, spe_id);
> }
> + case KVM_ARM_VCPU_SPE_INIT:
> + if (!vcpu_spe->irq_num)
> + return -ENXIO;
> +
> + if (!kvm_spe->spe_pmu)
> + return -ENXIO;
> +
> + if (!vgic_initialized(kvm))
> + return -ENXIO;
PMU returns -ENODEV in this case (+ documents it), worth keeping consistent with
that?
E.g.:
1.2 ATTRIBUTE: KVM_ARM_VCPU_PMU_V3_INIT
...
-ENODEV PMUv3 not supported or GIC not initialized
> +
> + if (kvm_vgic_set_owner(vcpu, vcpu_spe->irq_num, vcpu_spe))
This is getting an error then replacing it with -ENXIO, so probably better as:
int err;
...
err = kvm_vgic_set_owner(vcpu, vcpu_spe->irq_num, vcpu_spe);
if (err)
return err;
> + return -ENXIO;
> +
> + vcpu_spe->initialized = true;
> + return 0;
> }
>
> return -ENXIO;
> @@ -240,6 +269,7 @@ int kvm_spe_has_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
> switch(attr->attr) {
> case KVM_ARM_VCPU_SPE_IRQ:
> case KVM_ARM_VCPU_SPE_ID:
> + case KVM_ARM_VCPU_SPE_INIT:
> return 0;
> }
>
> --
> 2.43.0
>
>
--
Cheers, Lorenzo
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