linux-kernel - Re: [PATCH 0/2] PCI: Fix extended config space regression

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Message-ID: <20230111223055.GA1712775@bhelgaas>
Date:   Wed, 11 Jan 2023 16:30:55 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     linux-pci@...r.kernel.org
Cc:     Dan J Williams <dan.j.williams@...el.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        David E Box <david.e.box@...el.com>,
        Yunying Sun <yunying.sun@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Giovanni Cabiddu <giovanni.cabiddu@...el.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Hans de Goede <hdegoede@...hat.com>,
        Florent DELAHAYE <linuxkernelml@...ead.fr>,
        Konrad J Hambrick <kjhambrick@...il.com>,
        Matt Hansen <2lprbe78@...k.com>,
        Nicholas Johnson <nicholas.johnson-opensource@...look.com.au>,
        Benoit Grégoire <benoitg@...us.ca>,
        Werner Sembach <wse@...edocomputers.com>,
        mumblingdrunkard@...tonmail.com, linux-kernel@...r.kernel.org,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH 0/2] PCI: Fix extended config space regression

On Tue, Jan 10, 2023 at 12:02:41PM -0600, Bjorn Helgaas wrote:
> From: Bjorn Helgaas <bhelgaas@...gle.com>
> 
> 07eab0901ede ("efi/x86: Remove EfiMemoryMappedIO from E820 map") appeared
> in v6.2-rc1 and broke extended config space on several machines.
> 
> This broke drivers that use things in extended config space, e.g., perf,
> VSEC telemetry, EDAC, QAT, etc.
> 
> This happened because mmconfig-shared.c checks to see that ECAM space is
> reserved in E820 or ACPI motherboard resources.  If it's not, it assumes
> ECAM doesn't work.  07eab0901ede removed some E820 entries, so it looked
> like ECAM was no longer reserved, so we stopped using it.
> 
> The machines where this broke don't reserve the ECAM in ACPI PNP0C02
> devices (which seems to be what the PCI Firmware spec requires), but they
> do mention it in the EFI memory map as EfiMemoryMappedIO.
> 
> Bjorn Helgaas (2):
>   x86/pci: Simplify is_mmconf_reserved() messages
>   x86/pci: Treat EfiMemoryMappedIO as reservation of ECAM space
> 
>  arch/x86/pci/mmconfig-shared.c | 44 +++++++++++++++++++++++++++++-----
>  1 file changed, 38 insertions(+), 6 deletions(-)

Applied to for-linus for v6.2.  Sorry for the breakage and thank you
very much for the debugging and testing help!