From: "Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>
To: Rene Herman <rene.herman@keyaccess.nl>
CC: Ingo Molnar <mingo@elte.hu>, "Li, Shaohua" <shaohua.li@intel.com>,
       Dave Airlie <airlied@gmail.com>, Yinghai Lu <yhlu.kernel@gmail.com>,
       Andreas Herrmann <andreas.herrmann3@amd.com>,
       Arjan van de Ven <arjan@infradead.org>,
       Linux Kernel <linux-kernel@vger.kernel.org>,
       "Siddha, Suresh B" <suresh.b.siddha@intel.com>,
       Thomas Gleixner <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>,
       Dave Jones <davej@codemonkey.org.uk>
Date: Thu, 21 Aug 2008 15:57:35 -0700
Subject: RE: [PATCH] x86: {reverve,free}_memtype() take a physical address
Thread-Topic: [PATCH] x86: {reverve,free}_memtype() take a physical address
Thread-Index: AckD3N3RyEuIP9OvQCSGUEw8Vva9lAAARstA
Message-ID: <7E82351C108FA840AB1866AC776AEC460B4B047D@orsmsx505.amr.corp.intel.com>
References: <20080819102633.GE6722@elte.hu> <48AAD680.7020508@keyaccess.nl>
 <20080819190757.GA17470@linux-os.sc.intel.com>
 <20080820100440.GE28492@elte.hu> <48ABF6DC.8070305@keyaccess.nl>
 <48AC29CA.1060203@keyaccess.nl>
 <20080820194127.GA10887@linux-os.sc.intel.com>
 <48AC8F69.4050201@keyaccess.nl>
 <21d7e9970808201446k3c1a6bc1naf04568a8ad06ed4@mail.gmail.com>
 <20080820221630.GA3598@linux-os.sc.intel.com>
 <20080821120626.GG5615@elte.hu> <48ADA2C2.8090905@keyaccess.nl>
 <48ADE7C5.9030802@keyaccess.nl>
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In-Reply-To: <48ADEBB1.1070203@keyaccess.nl>
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>-----Original Message-----
>From: Rene Herman [mailto:rene.herman@keyaccess.nl]
>Sent: Thursday, August 21, 2008 3:27 PM
>To: Pallipadi, Venkatesh
>Cc: Ingo Molnar; Li, Shaohua; Dave Airlie; Yinghai Lu; Andreas
>Herrmann; Arjan van de Ven; Linux Kernel; Siddha, Suresh B;
>Thomas Gleixner; H. Peter Anvin; Dave Jones
>Subject: Re: [PATCH] x86: {reverve,free}_memtype() take a
>physical address
>
>On 22-08-08 00:16, Pallipadi, Venkatesh wrote:
>
>> Yes. Noticed that too and sent a patch here for x86/tip.
>>
>> http://www.ussg.iu.edu/hypermail/linux/kernel/0808.2/2270.html
>>
>> It is not very critical as it sounds as only set_memory_uc sets PAT
>> bits for RAM pages. Most other users (devmem mmap, ioramep, pci)
>> set PAT bits on the reserved memory. And there will not be conflicts
>> across RAM and reserveed regions. Regardless, this was a stupid
>> bug that we had missed earlier.
>
>And unfortunately I don't think the above fully fixes it for
>AGP. __pa()
>gets the real physical address and the memtypes should be on the GART
>remapped physical addresses it seems.
>

Page being marked here as uncached is the page got from alloc_page().
We are not really marking GART physical address as uncacheable. And
that page returned from alloc_page is what we are tracking with
reserve and free.
IOW, the tracking is only to keep CPU accesses consistent across
different va->pa and va across different CPUs and has nothing to do
with GART physical address here.

Thanks,
Venki
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