linux-kernel - Re: [PATCH v2 2/6] iommu: Configure default domain with def_domain

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Message-ID: <20200319140321.GA5122@8bytes.org>
Date:   Thu, 19 Mar 2020 15:03:21 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     ashok.raj@...el.com, jacob.jun.pan@...ux.intel.com,
        kevin.tian@...el.com,
        Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Daniel Drake <drake@...lessm.com>,
        Derrick Jonathan <jonathan.derrick@...el.com>,
        Jerry Snitselaar <jsnitsel@...hat.com>,
        Robin Murphy <robin.murphy@....com>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2 2/6] iommu: Configure default domain with
 def_domain_type

Hi Baolu,

On Sat, Mar 14, 2020 at 09:07:01AM +0800, Lu Baolu wrote:
> +static int iommu_group_change_def_domain(struct iommu_group *group, int type)
> +{
> +	struct group_device *grp_dev, *temp;
> +	struct iommu_domain *new, *old;
> +	const struct iommu_ops *ops;
> +	int ret = 0;
> +
> +	if ((type != IOMMU_DOMAIN_IDENTITY && type != IOMMU_DOMAIN_DMA) ||
> +	    !group->default_domain || type == group->default_domain->type ||
> +	    !group->default_domain->ops)
> +		return -EINVAL;
> +
> +	if (group->domain != group->default_domain)
> +		return -EBUSY;
> +
> +	iommu_group_ref_get(group);
> +	old = group->default_domain;
> +	ops = group->default_domain->ops;
> +
> +	/* Allocate a new domain of requested type. */
> +	new = ops->domain_alloc(type);
> +	if (!new) {
> +		ret = -ENOMEM;
> +		goto domain_out;
> +	}
> +	new->type = type;
> +	new->ops = ops;
> +	new->pgsize_bitmap = group->default_domain->pgsize_bitmap;
> +
> +	group->default_domain = new;
> +	group->domain = new;
> +	list_for_each_entry_safe(grp_dev, temp, &group->devices, list) {
> +		struct device *dev;
> +
> +		dev = grp_dev->dev;
> +		if (device_is_bound(dev)) {
> +			ret = -EINVAL;
> +			goto device_out;
> +		}
> +
> +		iommu_group_create_direct_mappings(group, dev);
> +		ret = __iommu_attach_device(group->domain, dev);
> +		if (ret)
> +			goto device_out;

In case of a failure here with a group containing multiple devices, the
other devices temporarily lose their mappings. Please only do the
device_is_bound() check in the loop and the actual re-attachment of the
group with a call to __iommu_attach_group().

Regards,

	Joerg