linux-kernel - Re: [RFC][PATCH 0/4] x86: ioremap() problem in X86

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Message-ID: <4C127531.90902@zytor.com>
Date:	Fri, 11 Jun 2010 10:41:05 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, jbarnes@...tuousgeek.org
Subject: Re: [RFC][PATCH 0/4] x86: ioremap() problem in X86_32 PAE

On 06/11/2010 02:17 AM, Kenji Kaneshige wrote:
> 
> By the way, I'm wondering some change might be needed also in PCI side.
> For example, current PCI subsystem disables 64-bit BAR with address
> higher than 32-bit assigned if sizeof(resource_size_t) is less than 8.
> But it doesn't care the case sizeof(resource_size_t) is equal to 8 on
> the system that cannot handle whole 64-bit physical address, like
> X86_32 PAE. In relation to this, my system is doing the following
> interesting behavior.
> 
> - On x86_32 without PAE, ioatdma works because 64-bit BAR is once
>   cleared and then lower address is assigned again.
> 
> - On x86_32 with PAE, ioatdma doesn' work even with my patch set.
>   Without my patch, kernel hangup or panic happens. With my patch,
>   ioatdma driver fails to initialize the device because ioremap()
>   returns NULL.
> 
> Anyway, I think ioremap() problem needs to be fixed first.
> 

We had a patch in for a while to cap the physical address space to the
number of bits supported by the CPU.  It got removed because it caused a
regression, which turned out to be because it exposed another bug (which
has since been fixed) -- I have been meaning to put it back in.

	-hpa
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