linux-kernel - Re: [PATCH] x86/PCI: never allocate PCI space from the last 1M below 4G

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Date:	Mon, 29 Nov 2010 18:36:20 +0000
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	Bjorn Helgaas <bjorn.helgaas@...com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] x86/PCI: never allocate PCI space from the last 1M
	below 4G

On Mon, Nov 29, 2010 at 11:30:09AM -0700, Bjorn Helgaas wrote:
> 
> The last 1M before 4G contains the processor restart vector and usually
> the system ROM.  We don't know the actual ROM size; I chose 1M because
> that's how much Windows 7 appears to avoid.
> 
> Without this check, we can allocate PCI space that will never work.  On
> Matthew's HP 2530p, we put the Intel GTT "Flush Page" at the very last
> page, which causes a spontaneous power-off:
> 
>   pci_root PNP0A08:00: host bridge window [mem 0xfee01000-0xffffffff]
>   fffff000-ffffffff : Intel Flush Page (assigned by intel-gtt)
> 
> Reference: https://bugzilla.kernel.org/show_bug.cgi?id=23542
> Reported-by: Matthew Garrett <mjg@...hat.com>
> Signed-off-by: Bjorn Helgaas <bjorn.helgaas@...com>

Tested-by: Matthew Garrett <mjg@...hat.com>

-- 
Matthew Garrett | mjg59@...f.ucam.org
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