linux-kernel - Re: [rfc] hw resource debugging checks

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Message-ID: <86802c440804141111g7a0cad03rf0b46a9fff01fa95@mail.gmail.com>
Date:	Mon, 14 Apr 2008 11:11:32 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Arjan van de Ven" <arjan@...radead.org>
Cc:	"Andi Kleen" <andi@...stfloor.org>, "Ingo Molnar" <mingo@...e.hu>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Pavel Machek" <pavel@....cz>,
	"Thomas Gleixner" <tglx@...utronix.de>, "H. Anvin" <hpa@...or.com>,
	"Greg Kroah-Hartman" <gregkh@...e.de>
Subject: Re: [rfc] hw resource debugging checks

On Mon, Apr 14, 2008 at 7:12 AM, Arjan van de Ven <arjan@...radead.org> wrote:
> On Sun, 13 Apr 2008 22:01:23 -0700
>
>
> "Yinghai Lu" <yhlu.kernel@...il.com> wrote:
>
>  > On Sun, Apr 13, 2008 at 8:52 PM, Arjan van de Ven
>  > <arjan@...radead.org> wrote:
>  > >
>  > > On Sun, 13 Apr 2008 12:29:30 -0700
>  > >  "Yinghai Lu" <yhlu.kernel@...il.com> wrote:
>  > >
>  > >  > On Sun, Apr 13, 2008 at 11:29 AM, Andi Kleen
>  > >  > <andi@...stfloor.org> wrote:
>  > >  > > > even I could talk to BIOS
>  > >  > >  > engineers everyday and tell them how to fix the problem in
>  > >  > >  > BIOS,  some still can not be fixed because of the legacy
>  > >  > >  > BIOS framework or big mess.
>  > >  > >
>  > >  > >  ... so you opt to create the big mess in the kernel. Great.
>  > >  > >
>  > >  > >  And it does not even fixes a real problem, but getting
>  > >  > >  mmconfig or the numa bus discovery to work is not really a too
>  > >  > > serious issue anyways. At best it is the icing on the cake to
>  > >  > > enable some relatively obscure functionality and be a little
>  > >  > > more efficient, but nothing really fundamental.
>  > >  > >
>  > >  > >  But for those things just expecting a working modern BIOS is
>  > >  > > quite reasonable.
>  > >  >
>  > >  > it does fix real problem. when big system with several HT links,
>  > >  > and every link some pcie slots.
>  > >  > you fully load pci-e cards (with pci bridge). BIOS will stop
>  > >  > assign io/mmio resource to left device if it run out of io port
>  > >  > range. (though it is supposed to go on to allocate mmio to left
>  > >  > devices) ( modern pcie device only need mmio with drivers)
>  > >  >
>  > >  > With pre set range allocation in NB pci conf, kernel could
>  > >  > allocate the resource in every peer root bus ranges.
>  > >  > (the code for assign resource to device that is not assigned
>  > >  > resource by BIOS --- already in kernel)
>  > >  >
>  > >
>  > >  there is a really big difference between assigning PCI device
>  > > resources and doing a whole thing like MMCFG from scratch.
>  > >
>  > that MCONF patchset for AMD fam10h include
>  > 1. get mmconfig from MSR, MCFG is using that too, if that is right,
>  > and we will get MCONF support when acpi support is off, and MCFG is
>  > broken.
>  > 2. or assign 0xfc00000000 to that MSR, that is safe too.
>
>  using MCONF when the ACPI support isn't there is just a deathtrap.
>  To be honest, if you want to break the AMD machines out there, who am
>  I to care about that, I work for Intel. But I'm worried someone thinks
>  this can be done for Intel based systems too, and then carry over all
>  the bad bugs to those as well ;(

I don't want to break any machine. and just want to workaround some
bios bug, and use MMCONF when acpi is disabled...

YH
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