linux-kernel - Re: [REGRESSION] Too-low frequency limit for AMD GPU PCI-passed-through to Windows VM

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Message-ID: <877d96to55.fsf@dmarc-none.turner.link>
Date:   Sun, 06 Mar 2022 21:12:52 -0500
From:   James Turner <linuxkernel.foss@...rc-none.turner.link>
To:     Thorsten Leemhuis <regressions@...mhuis.info>
Cc:     Alex Deucher <alexdeucher@...il.com>,
        "Lazar, Lijo" <lijo.lazar@....com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        "Koenig, Christian" <Christian.Koenig@....com>
Subject: Re: [REGRESSION] Too-low frequency limit for AMD GPU
 PCI-passed-through to Windows VM

Hi Thorsten,

My understanding at this point is that the root problem is probably not
in the Linux kernel but rather something else (e.g. the machine firmware
or AMD Windows driver) and that the change in
f9b7f3703ff9 ("drm/amdgpu/acpi: make ATPX/ATCS structures global (v2)")
simply exposed the underlying problem.

This week, I'll double-check that this is the case by disabling the
`amdgpu_atif_pci_probe_handle` function and testing again. I'll post the
results here.

James