linux-kernel - Re: [PATCH 2/2] x86/pci: Treat EfiMemoryMappedIO as reservation of ECAM space

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Date:   Tue, 21 Nov 2023 16:24:07 +0100
From:   Tomasz Pala <gotar@...anet.pl>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     linux-pci@...r.kernel.org,
        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>,
        Sebastian Manciulea <manciuleas@...tonmail.com>
Subject: Re: [PATCH 2/2] x86/pci: Treat EfiMemoryMappedIO as reservation of
 ECAM space

On Mon, Nov 20, 2023 at 10:29:33 -0600, Bjorn Helgaas wrote:

> Thank you!  A BIOS update is almost never the answer because even if
> an update exists, we have to assume that most users in the field will
> never install the update.

Not to mention enabling 64-bit BARs, which is even more cumbersome
ixgbe-specific magic that requires entirely dedicated tools...

>> .text .data .bss are not marked as E820_TYPE_RAM!
and
>> DMAR: [Firmware Bug]: No firmware reserved region can cover this RMRR [0x00000000df243000-0x00000000df251fff], contact BIOS vendor for fixes
>> DMAR: [Firmware Bug]: Your BIOS is broken; bad RMRR [0x00000000df243000-0x00000000df251fff]
[...]
> I think Linux basically converts the info from EFI GetMemoryMap
> to an e820 format; I think booting with "efi=debug" would show more
> details of this.

The dmesg I've attached today is with efi=debug, but the weird thing is
- both of the above warnings manifested themself only once, with the
first (verbose debugging: "MCFG debug") patch applied... Anyway.

The "memremap attempted on mixed range 0x0000000000000000 size: 0x8000
WARNING: CPU: 0 PID: 1 at kernel/iomem.c:78 memremap+0x154/0x170" also
seems to be triggered by "efi=debug", so my guess is that it's unrelated.

-- 
Tomasz Pala <gotar@...-linux.org>