Hi Connie,
On 4/14/25 6:38 PM, Cornelia Huck wrote:
> Add an helper to retrieve the writable id reg bitmask. The
> status of the query is stored in the CPU struct so that an
> an error, if any, can be reported on vcpu realize().
>
> Signed-off-by: Eric Auger <eric.au...@redhat.com>
> Signed-off-by: Cornelia Huck <coh...@redhat.com>
> ---
> target/arm/cpu.h | 26 ++++++++++++++++++++++++++
> target/arm/kvm.c | 32 ++++++++++++++++++++++++++++++++
> target/arm/kvm_arm.h | 7 +++++++
> 3 files changed, 65 insertions(+)
>
> diff --git a/target/arm/cpu.h b/target/arm/cpu.h
> index d27134f4a025..bbee7ff2414a 100644
> --- a/target/arm/cpu.h
> +++ b/target/arm/cpu.h
> @@ -856,6 +856,26 @@ typedef struct {
> uint32_t map, init, supported;
> } ARMVQMap;
>
> +typedef enum ARMIdRegsState {
> + WRITABLE_ID_REGS_UNKNOWN,
> + WRITABLE_ID_REGS_NOT_DISCOVERABLE,
> + WRITABLE_ID_REGS_FAILED,
> + WRITABLE_ID_REGS_AVAIL,
> +} ARMIdRegsState;
> +
> +/*
> + * The following structures are for the purpose of mapping the output of
> + * KVM_ARM_GET_REG_WRITABLE_MASKS that also may cover id registers we do
> + * not support in QEMU
> + * ID registers in op0==3, op1=={0,1,3}, crn=0, crm=={0-7}, op2=={0-7},
> + * as used by the KVM_ARM_GET_REG_WRITABLE_MASKS ioctl call.
> + */
> +#define NR_ID_REGS (3 * 8 * 8)
We may rename this define to better associate to the KVM API. I tend to
mix it with NUM_ID_IDX now ;-)
maybe something like KVM_NR_EXPOSED_ID_REGS
> +
> +typedef struct IdRegMap {
> + uint64_t regs[NR_ID_REGS];
> +} IdRegMap;
I would add a comment saying this is the mask array, just to prevent the
reading from thinking it is the actual reg content.
> +
> /* REG is ID_XXX */
> #define FIELD_DP64_IDREG(ISAR, REG, FIELD, VALUE) \
> ({ \
> @@ -1044,6 +1064,12 @@ struct ArchCPU {
> */
> bool host_cpu_probe_failed;
>
> + /*
> + * state of writable id regs query used to report an error, if any,
> + * on KVM custom vcpu model realize
> + */
> + ARMIdRegsState writable_id_regs;
maybe rename into writable_id_reg_status that would better reflect what
it is.
> +
> /* QOM property to indicate we should use the back-compat CNTFRQ default
> */
> bool backcompat_cntfrq;
>
> diff --git a/target/arm/kvm.c b/target/arm/kvm.c
> index 8491f42a18d2..6e3cd06e9bc5 100644
> --- a/target/arm/kvm.c
> +++ b/target/arm/kvm.c
> @@ -50,6 +50,7 @@ const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
> static bool cap_has_mp_state;
> static bool cap_has_inject_serror_esr;
> static bool cap_has_inject_ext_dabt;
> +static int cap_writable_id_regs;
>
> /**
> * ARMHostCPUFeatures: information about the host CPU (identified
> @@ -488,6 +489,37 @@ void kvm_arm_set_cpu_features_from_host(ARMCPU *cpu)
> env->features = arm_host_cpu_features.features;
> }
>
> +int kvm_arm_get_writable_id_regs(ARMCPU *cpu, IdRegMap *idregmap)
> +{
> + struct reg_mask_range range = {
> + .range = 0, /* up to now only a single range is supported */
> + .addr = (uint64_t)idregmap,
> + };
> + int ret;
> +
> + if (!kvm_enabled()) {
> + cpu->writable_id_regs = WRITABLE_ID_REGS_NOT_DISCOVERABLE;
> + return -ENOSYS;
> + }
> +
> + cap_writable_id_regs =
> + kvm_check_extension(kvm_state,
> KVM_CAP_ARM_SUPPORTED_REG_MASK_RANGES);
> +
> + if (!cap_writable_id_regs ||
> + !(cap_writable_id_regs & (1 << KVM_ARM_FEATURE_ID_RANGE))) {
> + cpu->writable_id_regs = WRITABLE_ID_REGS_NOT_DISCOVERABLE;
> + return -ENOSYS;
> + }
> +
> + ret = kvm_vm_ioctl(kvm_state, KVM_ARM_GET_REG_WRITABLE_MASKS, &range);
> + if (ret) {
> + cpu->writable_id_regs = WRITABLE_ID_REGS_FAILED;
> + return ret;
> + }
> + cpu->writable_id_regs = WRITABLE_ID_REGS_AVAIL;
> + return ret;
> +}
> +
> static bool kvm_no_adjvtime_get(Object *obj, Error **errp)
> {
> return !ARM_CPU(obj)->kvm_adjvtime;
> diff --git a/target/arm/kvm_arm.h b/target/arm/kvm_arm.h
> index 05c3de8cd46e..8d1f20ca8d89 100644
> --- a/target/arm/kvm_arm.h
> +++ b/target/arm/kvm_arm.h
> @@ -221,6 +221,8 @@ int kvm_arm_set_irq(int cpu, int irqtype, int irq, int
> level);
>
> void kvm_arm_enable_mte(Object *cpuobj, Error **errp);
>
> +int kvm_arm_get_writable_id_regs(ARMCPU *cpu, IdRegMap *idregmap);
> +
> #else
>
> /*
> @@ -247,6 +249,11 @@ static inline bool kvm_arm_mte_supported(void)
> return false;
> }
>
> +static inline int kvm_arm_get_writable_id_regs(ARMCPU *cpu, IdRegMap
> *idregmap)
> +{
> + return -ENOSYS;
> +}
> +
> /*
> * These functions should never actually be called without KVM support.
> */
Cheers
Eric
