linux-kernel - Re: [PATCH] x86/PCI: never allocate PCI MMIO resources below BIOS

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Message-ID: <2b1eecc3-75b8-4ab3-8932-fdf7cc1e181b@email.android.com>
Date:	Mon, 26 Apr 2010 16:02:57 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
CC:	Bjorn Helgaas <bjorn.helgaas@...com>,
	Andy Isaacson <adi@...apodia.org>,
	"R. Andrew Bailey" <bailey@...mai.com>,
	Yinghai <yinghai.lu@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, guenter.roeck@...csson.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Renninger <trenn@...e.de>, yaneti@...lera.com
Subject: Re: [PATCH] x86/PCI: never allocate PCI MMIO resources below   BIOS_END

I don't think it's sufficient, actually.  We regularly see machines where devices point into e820_reserved memory above 1 MB - because it's a platform device or because firmware (e.g. smm) is touching the device.  I think Bjorn's fix is great for .34, but longer term I think we need to structure the code to actually handle reserved regions differently from occupied/forbidden regions.

"Jesse Barnes" <jbarnes@...tuousgeek.org> wrote:

>On Mon, 26 Apr 2010 14:44:50 -0700
>"H. Peter Anvin" <hpa@...or.com> wrote:
>
>> >
>> > Agreed.  The trickier part is handling any platform devices that
>> > request_resource against that space.  But maybe we don't need to do
>> > anything special; just making sure we avoid it in the PCI "BIOS" code
>> > as Bjorn did may be sufficient.
>> >
>> 
>> Why is that hard?  If a platform device does a request_resource against
>> that space, it's a request for specific address space and it should be
>> granted.
>
>I was thinking if we made it a special resource type we'd have to
>change any platform drivers to use it; i.e. it wouldn't be
>IORESOURCE_MEM or IORESOURCE_IO but IORESOURCE_DRAGONS.  That way it
>wouldn't be part of the normal resource space.
>
>But that's definitely overkill.  I think Bjorn's fix is sufficient.
>
>-- 
>Jesse Barnes, Intel Open Source Technology Center

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