Re: [RFC PATCH v3 14/15] Read and validate host SMMUv3 feature bits

[Nicolin Chen <nicolinc@nvidia.com>]

On Mon, Jul 14, 2025 at 04:59:40PM +0100, Shameer Kolothum wrote:
> +void smmuv3_accel_init_regs(SMMUv3State *s)
> +{
> +    SMMUv3AccelState *s_accel = s->s_accel;
> +    SMMUv3AccelDevice *accel_dev;
> +    uint32_t data_type;
> +    uint32_t val;
> +    int ret;
> +
> +    if (s_accel->info.idr[0]) {
> +        /* We already got this */
> +        return;

We can avoid duplicated HW_INFO ioctls but probably shouldn't return
here, but just goto ..

> +    }
> +
> +    if (!s_accel->viommu || QLIST_EMPTY(&s_accel->viommu->device_list)) {
> +        error_report("For arm-smmuv3,accel=on case, atleast one cold-plugged "
> +                     "vfio-pci dev needs to be assigned");
> +        goto out_err;
> +    }
> +
> +    accel_dev = QLIST_FIRST(&s_accel->viommu->device_list);
> +    ret = smmuv3_accel_host_hw_info(accel_dev, &data_type,
> +                                    sizeof(s_accel->info), &s_accel->info);
> +    if (ret) {
> +        error_report("Failed to get Host SMMU device info");
> +        goto out_err;
> +    }
> +
> +    if (data_type != IOMMU_HW_INFO_TYPE_ARM_SMMUV3) {
> +        error_report("Wrong data type (%d) for Host SMMU device info",
> +                     data_type);
> +        goto out_err;
> +    }

.. likely here:

> +    trace_smmuv3_accel_host_hw_info(s_accel->info.idr[0], s_accel->info.idr[1],
> +                                    s_accel->info.idr[3], s_accel->info.idr[5]);

The following register initializations shouldn't be skipped.

Otherwise, caps would not be the same after a system reboot.

Thanks
Nicolin