Date: Thu, 6 Nov 2014 13:54:05 +0100
From: Joerg Roedel <jroedel@suse.de>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: Joerg Roedel <joro@8bytes.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        David Woodhouse <dwmw2@infradead.org>,
        Jiang Liu <jiang.liu@linux.intel.com>,
        iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        Myron Stowe <mstowe@redhat.com>
Subject: Re: [PATCH 2/2] iommu/vt-d: Only remove domain when device is removed
Message-ID: <20141106125405.GI8354@suse.de>
References: <1412074923-6342-1-git-send-email-joro@8bytes.org>
 <1412074923-6342-3-git-send-email-joro@8bytes.org>
 <1415117537.27420.428.camel@ul30vt.home>
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Hi Alex,

On Tue, Nov 04, 2014 at 09:12:17AM -0700, Alex Williamson wrote:
> I haven't tested it, but I'm concerned whether this has introduced a
> domain leak.  If we think about the case of unbinding a device from a
> host driver and attaching it to a domain through the IOMMU API, I think
> we used to count on this path to call domain_exit(), which made the
> domain_context_mapped() in intel_iommu_attach_device() "unlikely".  With
> this change, isn't the test in intel_iommu_attach_device() now neither
> likely nor unlikely and we're only removing the dev_info from the domain
> and not destroying the domain itself?  Thanks,

As I see it, there is no leak. The DMA-API domains are kept in the
device_domain_list and re-used when the device driver re-attaches. But
your are right that the unlikely in intel_iommu_attach_device() isn't
true anymore. We could probably remove it.


	Joerg

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