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xen-devel
Re: [Xen-devel] [PATCH] MTRR: clear DramModEn bit of sys_cfg MSR
Sorry for the indention issue... I agree that it is better to move
check-and_fixup code to init_amd() function. See the new patch.
My understanding is that RdMem and WrMem are never going to become 1:
BIOS are supposed to set sys_cfg[DramModEn] bit to 0 before OS takes
over. As a result, RdMem and WrMem are read as 0 in fixed MTRRs. Unless
Xen turn these bits to 1 (which I don't see from the code),
k8_enable_fixed_iorrs() is useless. My 2nd patch removes
k8_enable_fixed_iorrs(). If you have concern, we don't have to apply
this patch. But I don't think we shouldn't move it to amd.c.
k8_enable_fixed_iorrs() is unrelated in that file.
Thanks,
-Wei
On 04/05/2011 06:51 AM, Keir Fraser wrote:
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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amd_fix_syscfg.txt
Description: amd_fix_syscfg.txt
amd_remove_k8_enable_fixed_iorrs.txt
Description: amd_remove_k8_enable_fixed_iorrs.txt
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