linux-kernel - Re: [PATCH] x86, HPET: ignore any PCI BARs that match an HPET we already know about

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Message-ID: <4C9A7EDC.5030809@zytor.com>
Date:	Wed, 22 Sep 2010 15:10:36 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Bjorn Helgaas <bjorn.helgaas@...com>
CC:	Venkatesh Pallipadi <venki@...gle.com>,
	Prarit Bhargava <prarit@...hat.com>,
	Simon Arlott <simon@...e.lp0.eu>, x86@...nel.org,
	Clemens Ladisch <clemens@...isch.de>,
	linux-kernel@...r.kernel.org, Marc Jones <marcj303@...il.com>,
	Jordan Crouse <jcrouse@...eaurora.org>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86, HPET: ignore any PCI BARs that match an HPET we
 already know about

On 09/22/2010 02:52 PM, Bjorn Helgaas wrote:
> 
> We don't necessarily need to slavishly copy what Windows does, but
> I'd feel better if we understood how it avoided the problem on the
> Gigabyte board so we could make a more informed decision.
> 
> It really doesn't look like Windows, and therefore BIOS writers,
> share your expectations about PCI BARs in E820 reserved areas.
> It's likely still *safe* to make them fixed resources, but we might
> be able to fix more issues if we knew how Windows avoids the problem.
> 

Keep in mind that Windows -- the version they tested against -- might
just work by accident.  That's a "ship it" condition for the BIOS for
almost every vendor.

Also, do note that the reservations don't necessarily need to come from
the BIOS; we can mark the HPET area internally reserved, for example,
when we discover it.

	-hpa

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