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

From: Bjorn Helgaas <helgaas@kernel.org>
To: Tomasz Pala <gotar@polanet.pl>
Cc: linux-pci@vger.kernel.org,
	"Dan J Williams" <dan.j.williams@intel.com>,
	"Kan Liang" <kan.liang@linux.intel.com>,
	"Tony Luck" <tony.luck@intel.com>,
	"David E Box" <david.e.box@intel.com>,
	"Yunying Sun" <yunying.sun@intel.com>,
	"Dave Jiang" <dave.jiang@intel.com>,
	"Mika Westerberg" <mika.westerberg@linux.intel.com>,
	"Giovanni Cabiddu" <giovanni.cabiddu@intel.com>,
	"Herbert Xu" <herbert@gondor.apana.org.au>,
	"Hans de Goede" <hdegoede@redhat.com>,
	"Florent DELAHAYE" <linuxkernelml@undead.fr>,
	"Konrad J Hambrick" <kjhambrick@gmail.com>,
	"Matt Hansen" <2lprbe78@duck.com>,
	"Nicholas Johnson" <nicholas.johnson-opensource@outlook.com.au>,
	"Benoit Grégoire" <benoitg@coeus.ca>,
	"Werner Sembach" <wse@tuxedocomputers.com>,
	mumblingdrunkard@protonmail.com, linux-kernel@vger.kernel.org,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Sebastian Manciulea" <manciuleas@protonmail.com>
Subject: Re: [PATCH 2/2] x86/pci: Treat EfiMemoryMappedIO as reservation of ECAM space
Date: Tue, 21 Nov 2023 12:19:33 -0600	[thread overview]
Message-ID: <20231121181933.GA240494@bhelgaas> (raw)
In-Reply-To: <20231121152407.GA13288@polanet.pl>

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