From: Joerg Roedel <joerg.roedel@amd.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: <dwmw2@infradead.org>, <linux-pci@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <chrisw@sous-sol.org>,
<iommu@lists.linux-foundation.org>
Subject: Re: [PATCH v2] intel-iommu: Default to non-coherent for domains unattached to iommus
Date: Tue, 18 Sep 2012 13:58:02 +0200 [thread overview]
Message-ID: <20120918115802.GJ2505@amd.com> (raw)
In-Reply-To: <20111112002421.10875.8307.stgit@bling.home>
On Fri, Nov 11, 2011 at 05:26:44PM -0700, Alex Williamson wrote:
> domain_update_iommu_coherency() currently defaults to setting domains
> as coherent when the domain is not attached to any iommus. This
> allows for a window in domain_context_mapping_one() where such a
> domain can update context entries non-coherently, and only after
> update the domain capability to clear iommu_coherency.
>
> This can be seen using KVM device assignment on VT-d systems that
> do not support coherency in the ecap register. When a device is
> added to a guest, a domain is created (iommu_coherency = 0), the
> device is attached, and ranges are mapped. If we then hot unplug
> the device, the coherency is updated and set to the default (1)
> since no iommus are attached to the domain. A subsequent attach
> of a device makes use of the same dmar domain (now marked coherent)
> updates context entries with coherency enabled, and only disables
> coherency as the last step in the process.
>
> To fix this, switch domain_update_iommu_coherency() to use the
> safer, non-coherent default for domains not attached to iommus.
>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> Tested-by: Donald Dutile <ddutile@redhat.com>
> Acked-by: Donald Dutile <ddutile@redhat.com>
> Acked-by: Chris Wright <chrisw@sous-sol.org>
Applied, thanks.
--
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Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach
General Managers: Alberto Bozzo
Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632
prev parent reply other threads:[~2012-09-18 11:58 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-12 0:26 [PATCH v2] intel-iommu: Default to non-coherent for domains unattached to iommus Alex Williamson
2012-08-20 20:39 ` Craig Hada
2012-09-18 11:58 ` Joerg Roedel [this message]
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