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From:   Koba Ko <koba.ko@canonical.com>
Date:   Mon, 15 Jun 2020 11:46:50 +0800
Message-ID: <CAJB-X+VcHvYWngtMVHw5f_XaqA4i4T61yt=h7YvuD=eo3y7Rog@mail.gmail.com>
Subject: [Issue]platform/x86: iommu: System can't shutdown because iommu
 driver keeps checking the status of DMA_GSTS_TES
To:     David Woodhouse <dwmw2@infradead.org>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        Joerg Roedel <joro@8bytes.org>
Cc:     iommu@lists.linux-foundation.org,
        Kai Heng Feng <kai.heng.feng@canonical.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org
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hi All,
I have a machine and there's only intel gpu.
the secureboot and vt-d is enabled in BIOS.
On the Ubuntu desktop, I do s2idle first and restart the machine.
The machine can't restart successfully, so I need to press the power
button to shutdown.
I tried  each of the following and the issue can't be triggered.
1. disable secure boot in BIOS.
2. intel_iommu=off.
3. intel_iomm=igfx_off.
4. nomodeset
5. i915.modeset=0.

After I investigate further, find inte_iommu keeps checking the status
of DMA_GSTS_TES.
During the procedure of restart, the driver would disable iommu translation and
check the status of DMA_GSTS_TES until status of DMA_GSTS_TES is 0.

If you need more information, I can provide it.

Thanks
Koba Ko