linux-kernel - Re: [PATCH] iommu/vt-d: Fix VM domain ID leak

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Date:	Thu, 16 Jul 2015 19:03:57 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	iommu@...ts.linux-foundation.org, dwmw2@...radead.org,
	jiang.liu@...ux.intel.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu/vt-d: Fix VM domain ID leak

On Thu, Jul 16, 2015 at 09:43:55AM -0600, Alex Williamson wrote:
> I was tempted to do this as well, but what about
> domain_remove_dev_info() where we also handle vm domains specially and
> don't do a symmetric detach in both directions?  I started down that
> path but quickly found the code to fragile to make those kinds of
> changes.  Thanks,

Okay, so domain_remove_dev_info() does:

                if (domain_type_is_vm(domain)) {
                        iommu_detach_dependent_devices(info->iommu, info->dev);
                        domain_detach_iommu(domain, info->iommu);
                }

... in a loop over all devices attached to the domain. The first
function (iommu_detach_dependent_devices) is not special to vm-domains.
In fact, domain_remove_one_dev_info calls it for all domain types.

And domain_detach_iommu only clears the bit in the iommu_bmp of the
domain, which is also not special and also called for all domain types
in domain_remove_one_dev_info.

So it looks like this special handling has no real purpose and is just
part of the whole mess. I am currently working on the conversion of the
Intel VT-d driver to use default-domains from the iommu-core. When this
is done we can get rid of that mess.

	Joerg

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