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Date:   Mon, 13 Jul 2020 10:01:15 +0200
From:   Joerg Roedel <joro@8bytes.org>
To:     Bjorn Helgaas <helgaas@kernel.org>
Cc:     Rajat Jain <rajatxjain@gmail.com>, Rajat Jain <rajatja@google.com>,
        "Raj, Ashok" <ashok.raj@intel.com>,
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        Lu Baolu <baolu.lu@linux.intel.com>,
        Bjorn Helgaas <bhelgaas@google.com>,
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        "Krishnakumar, Lalithambika" <lalithambika.krishnakumar@intel.com>,
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        Heikki Krogerus <heikki.krogerus@linux.intel.com>
Subject: Re: [PATCH v4 4/4] PCI/ACS: Enable PCI_ACS_TB for
 untrusted/external-facing devices
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On Sat, Jul 11, 2020 at 09:58:38PM -0500, Bjorn Helgaas wrote:
> If BIOS handed off with ATS enabled and we somehow relied on it being
> already enabled, something might break if we start disabling ATS.
> Just a theoretical possibility, doesn't seem likely to me.

I don't think this will be a problem. When the BIOS enables ATS for a
device it also needs to enable the IOMMU already, an we are not handling
an already enabled IOMMU (outside of kdump kernels) very well.


Regards,

	Joerg