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xen-devel
[Xen-devel] Re: [GIT PULL] xen /proc/mtrr implementation
To: |
Andi Kleen <andi@xxxxxxxxxxxxxx> |
Subject: |
[Xen-devel] Re: [GIT PULL] xen /proc/mtrr implementation |
From: |
"H. Peter Anvin" <hpa@xxxxxxxxx> |
Date: |
Wed, 20 May 2009 16:03:23 -0700 |
Cc: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, the arch/x86 maintainers <x86@xxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx>, "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx> |
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Andi Kleen wrote:
>>> Is this new interface only defined for swiotlb or MMIO mappings?
>>> If yes did you check the drivers only actually set it on
>>> swiotlb or MMIO (that seems dubious to me)?
>> Really? Do we ever set unusual memory types on normal system memory?
>
> There were drivers at some point that set WC MTRRs on their
> transfer rings, not mmio.
>
> Maybe these all switched to PAT now, maybe not
Most of those that I've heard of use WB memory and CLFLUSH.
The ones I know of which marked descriptor rings WB were ones which had
descriptor rings in MMIO space (which makes sense: MMIO reads are fully
synchronizing, but writes can be posted and write combined.)
-hpa
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