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

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Message-ID: <20231121181933.GA240494@bhelgaas>
Date:   Tue, 21 Nov 2023 12:19:33 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Tomasz Pala <gotar@...anet.pl>
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 Tue, Nov 21, 2023 at 04:24:07PM +0100, Tomasz Pala wrote:
> 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.

OK.  I don't know what (if anything) to do about the above.

> 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.

Yes, I think so.  This is from efi_debugfs_init(), which we only run
when "efi=debug", and I think it comes from memremapping this area:

  efi: mem00: [Boot Code   |   |  |  |  |  |  |  |  |  |   |WB|WT|WC|UC] range=[0x0000000000000000-0x0000000000007fff] (0MB)

Bjorn