Re: [PATCH 07/13] KVM: arm64: selftests: Provide helper for getting default vCPU target

Itaru Kitayama
2025-09-17T21:56:51Z

On Wed, Sep 17, 2025 at 02:20:37PM -0700, Oliver Upton wrote:
> The default vCPU target in KVM selftests is pretty boring in that it
> doesn't enable any vCPU features. Expose a helper for getting the
> default target to prepare for cramming in more features. Call
> KVM_ARM_PREFERRED_TARGET directly from get-reg-list as it needs
> fine-grained control over feature flags.
>
> Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
> ---
> tools/testing/selftests/kvm/arm64/psci_test.c | 2 +-
> .../testing/selftests/kvm/arm64/smccc_filter.c | 2 +-
> .../selftests/kvm/arm64/vpmu_counter_access.c | 4 ++--
> tools/testing/selftests/kvm/get-reg-list.c | 9 ++++++---
> .../selftests/kvm/include/arm64/processor.h | 2 ++
> .../testing/selftests/kvm/lib/arm64/processor.c | 17 +++++++++++------
> 6 files changed, 23 insertions(+), 13 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/arm64/psci_test.c b/tools/testing/selftests/kvm/arm64/psci_test.c
> index cf208390fd0e..0d4680da66d1 100644
> --- a/tools/testing/selftests/kvm/arm64/psci_test.c
> +++ b/tools/testing/selftests/kvm/arm64/psci_test.c
> @@ -89,7 +89,7 @@ static struct kvm_vm *setup_vm(void *guest_code, struct kvm_vcpu **source,
>
> vm = vm_create(2);
>
> - vm_ioctl(vm, KVM_ARM_PREFERRED_TARGET, &init);
> + kvm_get_default_vcpu_target(vm, &init);
> init.features[0] |= (1 << KVM_ARM_VCPU_PSCI_0_2);
>
> *source = aarch64_vcpu_add(vm, 0, &init, guest_code);

I wonder if the ioctl() can be called unconditionally in the
aarch64_vcpu_add() function. If the intention is that the kvm selftest
code needs to write this way I am fine with that.

Reviewed-by: Itaru Kitayama <itaru.kitayama@fujitsu.com>

> diff --git a/tools/testing/selftests/kvm/arm64/smccc_filter.c b/tools/testing/selftests/kvm/arm64/smccc_filter.c
> index eb5551d21dbe..a8e22d866ea7 100644
> --- a/tools/testing/selftests/kvm/arm64/smccc_filter.c
> +++ b/tools/testing/selftests/kvm/arm64/smccc_filter.c
> @@ -64,7 +64,7 @@ static struct kvm_vm *setup_vm(struct kvm_vcpu **vcpu)
> struct kvm_vm *vm;
>
> vm = vm_create(1);
> - vm_ioctl(vm, KVM_ARM_PREFERRED_TARGET, &init);
> + kvm_get_default_vcpu_target(vm, &init);
>
> /*
> * Enable in-kernel emulation of PSCI to ensure that calls are denied
> diff --git a/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c b/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c
> index 36a3a8b4e0b5..2a8f31c8e59f 100644
> --- a/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c
> +++ b/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c
> @@ -430,7 +430,7 @@ static void create_vpmu_vm(void *guest_code)
> }
>
> /* Create vCPU with PMUv3 */
> - vm_ioctl(vpmu_vm.vm, KVM_ARM_PREFERRED_TARGET, &init);
> + kvm_get_default_vcpu_target(vpmu_vm.vm, &init);
> init.features[0] |= (1 << KVM_ARM_VCPU_PMU_V3);
> vpmu_vm.vcpu = aarch64_vcpu_add(vpmu_vm.vm, 0, &init, guest_code);
> vcpu_init_descriptor_tables(vpmu_vm.vcpu);
> @@ -525,7 +525,7 @@ static void run_access_test(uint64_t pmcr_n)
> * Reset and re-initialize the vCPU, and run the guest code again to
> * check if PMCR_EL0.N is preserved.
> */
> - vm_ioctl(vpmu_vm.vm, KVM_ARM_PREFERRED_TARGET, &init);
> + kvm_get_default_vcpu_target(vpmu_vm.vm, &init);
> init.features[0] |= (1 << KVM_ARM_VCPU_PMU_V3);
> aarch64_vcpu_setup(vcpu, &init);
> vcpu_init_descriptor_tables(vcpu);
> diff --git a/tools/testing/selftests/kvm/get-reg-list.c b/tools/testing/selftests/kvm/get-reg-list.c
> index 91f05f78e824..f4644c9d2d3b 100644
> --- a/tools/testing/selftests/kvm/get-reg-list.c
> +++ b/tools/testing/selftests/kvm/get-reg-list.c
> @@ -116,10 +116,13 @@ void __weak finalize_vcpu(struct kvm_vcpu *vcpu, struct vcpu_reg_list *c)
> }
>
> #ifdef __aarch64__
> -static void prepare_vcpu_init(struct vcpu_reg_list *c, struct kvm_vcpu_init *init)
> +static void prepare_vcpu_init(struct kvm_vm *vm, struct vcpu_reg_list *c,
> + struct kvm_vcpu_init *init)
> {
> struct vcpu_reg_sublist *s;
>
> + vm_ioctl(vm, KVM_ARM_PREFERRED_TARGET, init);
> +
> for_each_sublist(c, s)
> if (s->capability)
> init->features[s->feature / 32] |= 1 << (s->feature % 32);
> @@ -127,10 +130,10 @@ static void prepare_vcpu_init(struct vcpu_reg_list *c, struct kvm_vcpu_init *ini
>
> static struct kvm_vcpu *vcpu_config_get_vcpu(struct vcpu_reg_list *c, struct kvm_vm *vm)
> {
> - struct kvm_vcpu_init init = { .target = -1, };
> + struct kvm_vcpu_init init;
> struct kvm_vcpu *vcpu;
>
> - prepare_vcpu_init(c, &init);
> + prepare_vcpu_init(vm, c, &init);
> vcpu = __vm_vcpu_add(vm, 0);
> aarch64_vcpu_setup(vcpu, &init);
>
> diff --git a/tools/testing/selftests/kvm/include/arm64/processor.h b/tools/testing/selftests/kvm/include/arm64/processor.h
> index 5a4b29c1b965..87f50efed720 100644
> --- a/tools/testing/selftests/kvm/include/arm64/processor.h
> +++ b/tools/testing/selftests/kvm/include/arm64/processor.h
> @@ -357,4 +357,6 @@ static __always_inline u64 ctxt_reg_alias(struct kvm_vcpu *vcpu, u32 encoding)
> return KVM_ARM64_SYS_REG(alias);
> }
>
> +void kvm_get_default_vcpu_target(struct kvm_vm *vm, struct kvm_vcpu_init *init);
> +
> #endif /* SELFTEST_KVM_PROCESSOR_H */
> diff --git a/tools/testing/selftests/kvm/lib/arm64/processor.c b/tools/testing/selftests/kvm/lib/arm64/processor.c
> index 311660a9f655..5ae65fefd48c 100644
> --- a/tools/testing/selftests/kvm/lib/arm64/processor.c
> +++ b/tools/testing/selftests/kvm/lib/arm64/processor.c
> @@ -267,19 +267,24 @@ void virt_arch_dump(FILE *stream, struct kvm_vm *vm, uint8_t indent)
> }
> }
>
> +void kvm_get_default_vcpu_target(struct kvm_vm *vm, struct kvm_vcpu_init *init)
> +{
> + struct kvm_vcpu_init preferred = {};
> +
> + vm_ioctl(vm, KVM_ARM_PREFERRED_TARGET, &preferred);
> +
> + *init = preferred;
> +}
> +
> void aarch64_vcpu_setup(struct kvm_vcpu *vcpu, struct kvm_vcpu_init *init)
> {
> struct kvm_vcpu_init default_init = { .target = -1, };
> struct kvm_vm *vm = vcpu->vm;
> uint64_t sctlr_el1, tcr_el1, ttbr0_el1;
>
> - if (!init)
> + if (!init) {
> + kvm_get_default_vcpu_target(vm, &default_init);
> init = &default_init;
> -
> - if (init->target == -1) {
> - struct kvm_vcpu_init preferred;
> - vm_ioctl(vm, KVM_ARM_PREFERRED_TARGET, &preferred);
> - init->target = preferred.target;
> }
>
> vcpu_ioctl(vcpu, KVM_ARM_VCPU_INIT, init);
> --
> 2.47.3
>