linux-kernel - Re: [PATCH] x86/PCI: Revert: "Clip only host bridge windows for E820 regions"

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Message-ID: <Yqh+9Ei5BLhKB/da@smile.fi.intel.com>
Date:   Tue, 14 Jun 2022 15:28:36 +0300
From:   Andy Shevchenko <andriy.shevchenko@...el.com>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     "Rafael J . Wysocki" <rafael@...nel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Myron Stowe <myron.stowe@...hat.com>,
        Juha-Pekka Heikkila <juhapekka.heikkila@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Benoit Grégoire <benoitg@...us.ca>,
        Hui Wang <hui.wang@...onical.com>, linux-acpi@...r.kernel.org,
        linux-pci@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        "Guilherme G . Piccoli" <gpiccoli@...lia.com>
Subject: Re: [PATCH] x86/PCI: Revert: "Clip only host bridge windows for E820
 regions"

On Sun, Jun 12, 2022 at 04:43:25PM +0200, Hans de Goede wrote:
> Clipping the bridge windows directly from pci_acpi_root_prepare_resources()
> instead of clipping from arch_remove_reservations(), has a number of
> unforseen consequences.
> 
> If there is an e820 reservation in the middle of a bridge window, then
> the smallest of the 2 remaining parts of the window will be also clipped
> off. Where as the previous code would clip regions requested by devices,
> rather then the entire window, leaving regions which were either entirely
> above or below a reservation in the middle of the window alone.
> 
> E.g. on the Steam Deck this leads to this log message:
> 
> acpi PNP0A08:00: clipped [mem 0x80000000-0xf7ffffff window] to [mem 0xa0100000-0xf7ffffff window]
> 
> which then gets followed by these log messages:
> 
> pci 0000:00:01.2: can't claim BAR 14 [mem 0x80600000-0x806fffff]: no compatible bridge window
> pci 0000:00:01.3: can't claim BAR 14 [mem 0x80500000-0x805fffff]: no compatible bridge window
> 
> and many more of these. Ultimately this leads to the Steam Deck
> no longer booting properly, so revert the change.
> 
> Note this is not a clean revert, this revert keeps the later change
> to make the clipping dependent on a new pci_use_e820 bool, moving
> the checking of this bool to arch_remove_reservations().

It does _not_ fix the Intel MID case. It requires to have my patch applied as well.
So the difference as I see is the flags checking. I believe that you still need to
have it in case pci_use_e820 == true. But it might be that I missed an importan
detail.

-- 
With Best Regards,
Andy Shevchenko