linux-kernel - Re: [PATCH v2 0/3] x86/PCI: Log E820 clipping

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Date:   Tue, 19 Apr 2022 11:59:17 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Bjorn Helgaas <helgaas@...nel.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>
Cc:     Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Myron Stowe <myron.stowe@...hat.com>,
        Juha-Pekka Heikkila <juhapekka.heikkila@...il.com>,
        Benoit Grégoire <benoitg@...us.ca>,
        Hui Wang <hui.wang@...onical.com>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        linux-acpi@...r.kernel.org, linux-pci@...r.kernel.org,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v2 0/3] x86/PCI: Log E820 clipping

Hi All,

On 1/1/70 01:00, Bjorn Helgaas wrote:
> This is still work-in-progress on the issue of PNP0A03 _CRS methods that
> are buggy or not interpreted correctly by Linux.
> 
> The previous try at:
>   https://lore.kernel.org/r/20220304035110.988712-1-helgaas@kernel.org
> caused regressions on some Chromebooks:
>   https://lore.kernel.org/r/Yjyv03JsetIsTJxN@sirena.org.uk
> 
> This v2 drops the commit that caused the Chromebook regression, so it also
> doesn't fix the issue we were *trying* to fix on Lenovo Yoga and Clevo
> Barebones.
> 
> The point of this v2 update is to split the logging patch into (1) a pure
> logging addition and (2) the change to only clip PCI windows, which was
> previously hidden inside the logging patch and not well documented.
> 
> Bjorn Helgaas (3):
>   x86/PCI: Eliminate remove_e820_regions() common subexpressions
>   x86: Log resource clipping for E820 regions
>   x86/PCI: Clip only host bridge windows for E820 regions

Thanks, the entire series looks good to me:

Reviewed-by: Hans de Goede <hdegoede@...hat.com>

For the series.

So what is the plan to actually fix the issue seen on some Lenovo models
and Clevo Barebones ?   As I mentioned previously I think that since all
our efforts have failed so far that we should maybe reconsider just
using DMI quirks to ignore the E820 reservation windows for host bridges
on affected models ?

That or implement 3 of:

> So I think the progression is:
>
>  1) Remove anything mentioned in E820 from _CRS (4dc2287c1805 [7]).
>     This worked around some issues on Dell systems.
>
>  2) Remove things mentioned in E820 unless they cover the entire
>     window (5949965ec934 [8])
>
>  3) Coalesce adjacent _CRS windows, *then* remove things mentioned in
>     E820 unless they cover the entire (coalesced) window (current
>     proposal)

Regards,

Hans