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SubjectRe: [PATCH v5 2/8] iommu/vt-d: Add per-device IOMMU feature ops entries
Hi,

this looks a bit confusing to me because I can see no checking whether
the device actually supports scalable mode. More below:

On Thu, Jan 10, 2019 at 11:00:21AM +0800, Lu Baolu wrote:
> +static int intel_iommu_enable_auxd(struct device *dev)
> +{
> + struct device_domain_info *info;
> + struct dmar_domain *domain;
> + unsigned long flags;
> +
> + if (!scalable_mode_support())
> + return -ENODEV;
> +
> + domain = get_valid_domain_for_dev(dev);
> + if (!domain)
> + return -ENODEV;
> +
> + spin_lock_irqsave(&device_domain_lock, flags);
> + info = dev->archdata.iommu;
> + info->auxd_enabled = 1;
> + spin_unlock_irqrestore(&device_domain_lock, flags);
> +
> + return 0;
> +}

This code sets a flag to mark scalable mode enabled. Doesn't the device
need some handling too, like enabling the PASID capability and all?

> +
> +static bool
> +intel_iommu_dev_has_feat(struct device *dev, enum iommu_dev_features feat)
> +{
> + struct device_domain_info *info = dev->archdata.iommu;
> +
> + if (feat == IOMMU_DEV_FEAT_AUX)
> + return scalable_mode_support() && info && info->auxd_enabled;
> +
> + return false;
> +}

Why is this checking the auxd_enabled flag? The function should just
return whether the device _supports_ scalable mode, not whether it is
enabled.

Regards,

Joerg

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