linux-kernel - Re: [PATCH 1/2] x86, ioapic: Reserve only 128 bytes for IOAPICs

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Message-ID: <20110826064838.GB3903@sun>
Date:	Fri, 26 Aug 2011 10:48:38 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Ralf Jung <ralfjung-e@....de>,
	Yinghai Lu <yinghai@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] x86, ioapic: Reserve only 128 bytes for IOAPICs

On Thu, Aug 25, 2011 at 06:41:57PM -0700, H. Peter Anvin wrote:
> On 08/25/2011 05:17 PM, Bjorn Helgaas wrote:
> > 
> > If the OS allocated the next 128 bytes to another device, it sounds
> > like it would cause a conflict on Intel boxes.  This must be an area
> > that differs between vendors.  I haven't seen a spec that mentions 256
> > bytes as the required minimum MMIO size for IOAPICs, and apparently
> > the AMD IOAPIC decodes 240 bytes or fewer.
> > 
> 
> For what it's worth, it's probably a bad idea on x86 for the OS to
> allocate addresses in the 0xFExxxxxx range...
> 
> 	-hpa
> 

I rather wonder if there a way to assign a different address for the
watchdog Bjorn referring to. I don't have such machine to test but
seems its base address is configurable via pmio. Just curious.

	Cyrill
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