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Re: [PATCH -v1] MIPS: fix pfn_valid() for FLATMEM

To: Ralf Baechle <>
Subject: Re: [PATCH -v1] MIPS: fix pfn_valid() for FLATMEM
From: Wu Zhangjin <>
Date: Wed, 14 Oct 2009 09:06:13 +0800
Cc: "Rafael J. Wysocki" <>,, Sergei Shtylyov <>, Pavel Machek <>
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Organization: DSLab, Lanzhou University, China
Original-recipient: rfc822;
References: <> <> <> <1255054108.5810.74.camel@falcon> <1255104130.3658.122.camel@falcon> <>
On Wed, 2009-10-14 at 00:04 +0200, Ralf Baechle wrote:
> On Sat, Oct 10, 2009 at 12:02:10AM +0800, Wu Zhangjin wrote:
> > The above patch can not fix the problem when enabled FLATMEM in
> > linux-2.6.32-rc3, the real problem should be that we need register the
> > "pci memory space" as nosave pages, and also, the above "reserved"(not
> > memory) pages should be registered as nosave pages. but the simpler
> > solution should be the pfn_valid() I sent out in this E-mail thread, we
> > just need to check whether they are "valid", if they are "System
> > RAM"(BOOT_MEM_RAM or BOOT_MEM_ROM_DATA), they should be valid.
> > 
> > and what's more? should be register "pci memory space" as nosave pages
> > for all architecture?
> No.  You only see this problem because your PCI memory space is between
> the lowest and the highest memory address.  Other systems don't have this
> issue because they either use the discontig or sparse memory models.
> Btw, for systems that actually have memory in the 90000000-bfffffff range
> and are running a 64-bit kernel with 4k ages the flatmem memory model
> will waste 28MB of RAM; with 16k pages it's still 7MB.
> Time to say gooebye to flatmem?

Okay, I will enable SPARSEMEM by default in the defconfig later.

        Wu Zhangjin

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