linux-kernel - AMD IOMMU + SME + amdgpu regression

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Date:   Thu, 11 Jun 2020 19:05:21 -0400
From:   "Alex Xu (Hello71)" <alex_y_xu@...oo.ca>
To:     Joerg Roedel <joro@...tes.org>, linux-kernel@...r.kernel.org,
        David Rientjes <rientjes@...gle.com>,
        Christoph Hellwig <hch@....de>
Cc:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Rob Clark <robdclark@...il.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Gerald Schaefer <gerald.schaefer@...ibm.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Daniel Drake <drake@...lessm.com>, jonathan.derrick@...el.com,
        linux-samsung-soc@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-mediatek@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-tegra@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        Joerg Roedel <jroedel@...e.de>
Subject: AMD IOMMU + SME + amdgpu regression

Hi,

amdgpu + IOMMU + SME is now working for me on 5.7, yay! But, it is 
broken on torvalds master, boo. On boot, depending on which exact commit 
I test, it either hangs immediately (with built-in driver, before 
starting initramfs), displays some errors then hangs, or spams the 
screen with many amdgpu errors.

I bisected the black screen hang to:

commit dce8d6964ebdb333383bacf5e7ab8c27df151218
Author: Joerg Roedel <jroedel@...e.de>
Date:   Wed Apr 29 15:36:53 2020 +0200

    iommu/amd: Convert to probe/release_device() call-backs

    Convert the AMD IOMMU Driver to use the probe_device() and
    release_device() call-backs of iommu_ops, so that the iommu core code
    does the group and sysfs setup.

    Signed-off-by: Joerg Roedel <jroedel@...e.de>
    Link: https://lore.kernel.org/r/20200429133712.31431-16-joro@8bytes.org
    Signed-off-by: Joerg Roedel <jroedel@...e.de>

Testing torvalds master (623f6dc593) with the containing merge 
(98bdc74b36) plus the DMA mapping merge (4e94d08734) reverted allows 
amdgpu + IOMMU + SME to once again work.

I think that nobody is really working on amdgpu + SME, but it would be a 
shame if it was supported and then incidentally broken by a small 
change.

I am using an ASRock B450 Pro4 with Ryzen 1600 and ASUS RX 480. I don't 
understand this code at all, but let me know what I can do to 
troubleshoot.

Thanks,
Alex.