Re: [PATCH v3 09/10] arm-qmp-cmds: introspection for ID register props

[Eric Auger <eric.auger@redhat.com>]

On 4/14/25 6:38 PM, Cornelia Huck wrote:
> Implement the capability to query available ID register values by
> adding SYSREG_* options and values to the cpu model expansion for the
> host model, if available.
>
> Excerpt:
> (QEMU) query-cpu-model-expansion type=full model={"name":"host"}
> {"return": {"model": {"name": "host", "props":
> {"SYSREG_ID_AA64PFR0_EL1_EL3": 1224979098931106066,
> "SYSREG_ID_AA64ISAR2_EL1_CLRBHB": 0,
> ../..
>
> So this allows the upper stack to detect available writable ID
> regs and the "host passthrough model" values.
>
> [CH: moved SYSREG_* values to host model]
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
>
> ---
>
> TODO: Add the moment there is no way to test changing a given
> ID reg field value. ie:
>
> (QEMU) query-cpu-model-expansion type=full model={"name":"host", "prop":{"SYSREG_ID_AA64ISAR0_EL1_DP":0x13}}
Isn't it a mandated feature for layered products to be able to try a
given combination. Do you think this would be achievable?

Eric
> ---
>  target/arm/arm-qmp-cmds.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
>
> diff --git a/target/arm/arm-qmp-cmds.c b/target/arm/arm-qmp-cmds.c
> index 883c0a0e8cce..5f48c7d835e1 100644
> --- a/target/arm/arm-qmp-cmds.c
> +++ b/target/arm/arm-qmp-cmds.c
> @@ -21,6 +21,7 @@
>   */
>  
>  #include "qemu/osdep.h"
> +#include "qemu/error-report.h"
>  #include "hw/boards.h"
>  #include "kvm_arm.h"
>  #include "qapi/error.h"
> @@ -209,6 +210,24 @@ CpuModelExpansionInfo *qmp_query_cpu_model_expansion(CpuModelExpansionType type,
>          }
>      }
>  
> +    /* If writable ID regs are supported, add them as well */
> +    if (ARM_CPU(obj)->writable_id_regs == WRITABLE_ID_REGS_AVAIL) {
> +        ObjectProperty *prop;
> +        ObjectPropertyIterator iter;
> +
> +        object_property_iter_init(&iter, obj);
> +
> +        while ((prop = object_property_iter_next(&iter))) {
> +            QObject *value;
> +
> +            if (!g_str_has_prefix(prop->name, "SYSREG_")) {
> +                continue;
> +            }
> +            value = object_property_get_qobject(obj, prop->name, &error_abort);
> +            qdict_put_obj(qdict_out, prop->name, value);
> +        }
> +    }
> +
>      if (!qdict_size(qdict_out)) {
>          qobject_unref(qdict_out);
>      } else {