linux-kernel - Re: [PATCH 1/1] x86/pci: Skip early E820 check for ECAM region

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Date: Thu, 18 Apr 2024 12:10:11 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc: linux-pci@...r.kernel.org, Mateusz Kaduk <mateusz.kaduk@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>, Tj <linux@....tj>,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	Hans de Goede <hdegoede@...hat.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
	stable@...r.kernel.org
Subject: Re: [PATCH 1/1] x86/pci: Skip early E820 check for ECAM region

On Wed, Apr 17, 2024 at 08:10:28PM -0700, Kuppuswamy Sathyanarayanan wrote:
> 
> On 4/17/24 1:40 PM, Bjorn Helgaas wrote:
> > From: Bjorn Helgaas <bhelgaas@...gle.com>
> >
> > Arul, Mateusz, Imcarneiro91, and Aman reported a regression caused by
> > 07eab0901ede ("efi/x86: Remove EfiMemoryMappedIO from E820 map").  On the
> > Lenovo Legion 9i laptop, that commit removes the area containing ECAM from
> > E820, which means the early E820 validation started failing, which meant we
> > didn't enable ECAM in the "early MCFG" path
> ...

> LGTM
> 
> Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>

Thanks for taking a look!

> > -	if (!early && !acpi_disabled) {
> > +	if (early) {
> > +
> > +		/*
> > +		 * Don't try to do this check unless configuration type 1
> > +		 * is available.  How about type 2?
> 
> I don't understand why above question is included in the comment. Do
> you think it is better to drop that part of the comment?

The "How about type 2?" questio was added by bb63b4219976 ("x86 pci:
remove checking type for mmconfig probe").  I only moved it and fixed
the capitalization and formatting.

> > -	/* Don't try to do this check unless configuration
> > -	   type 1 is available. how about type 2 ?*/
> > -	if (raw_pci_ops)
> > -		return is_mmconf_reserved(e820__mapped_all, cfg, dev,
> > -					  "E820 entry");
> > -
> >  	return false;
> >  }