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Re: [Xen-devel] [PATCH] MTRR: clear DramModEn bit of sys_cfg MSR

To: Wei Huang <wei.huang2@xxxxxxx>, "'xen-devel@xxxxxxxxxxxxxxxxxxx'" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] MTRR: clear DramModEn bit of sys_cfg MSR
From: Keir Fraser <keir@xxxxxxx>
Date: Tue, 05 Apr 2011 12:51:32 +0100
Delivery-date: Tue, 05 Apr 2011 04:52:31 -0700
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Thread-topic: [Xen-devel] [PATCH] MTRR: clear DramModEn bit of sys_cfg MSR
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On 04/04/2011 23:23, "Wei Huang" <wei.huang2@xxxxxxx> wrote:

> Some buggy BIOS might set sys_cfg DramModEn bit to 1, which can cause
> unexpected behavior on AMD platforms. This patch clears DramModEn bit.
> The patch was derived from upstream kernel patch (see
> https://patchwork.kernel.org/patch/11425/).

This patch also removes k8_enable_fixed_iorrs(), and it's not clear why.
That would at least belong in a separate patch, but I would think we don't
want to delete that code anyway.

The indentation is wrong (spaces in a file that is hard-tab-indented). And
the printk is probably unnecessary -- at most you should print it once
rather than potentially for every core brought up.

But further, I don't see why you need to hang off {get,set}_fixed_ranges at
all. Why not do this check-and-fixup in cpu/amd.c:init_amd()? It's a handy
early-cpu-bringup amd-specific function which is rather designed ofr this
kind of purpose. The k8_enable_fixed_iorrs() work could better be done in
the same place, too (perhaps move it in a separate patch?).

 -- Keir

> Signed-off-by: Wei Huang <wei.huang2@xxxxxxx>
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