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SubjectRe: [PATCH 04/35] dmem: let pat recognize dmem
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On 08/10/20 09:53, yulei.kernel@gmail.com wrote:
> From: Yulei Zhang <yuleixzhang@tencent.com>
>
> x86 pat uses 'struct page' by only checking if it's system ram,
> however it is not true if dmem is used, let's teach pat to
> recognize this case if it is ram but it is !pfn_valid()
>
> We always use WB for dmem and any attempt to change this
> behavior will be rejected and WARN_ON is triggered
>
> Signed-off-by: Xiao Guangrong <gloryxiao@tencent.com>
> Signed-off-by: Yulei Zhang <yuleixzhang@tencent.com>

Hooks like these will make it very hard to merge this series.

I like the idea of struct page-backed memory, but this is a lot of code
and I wonder if it's worth adding all these complications.

One can already use mem= to remove the "struct page" cost for most of
the host memory, and manage the allocation of the remaining memory in
userspace with /dev/mem. What is the advantage of doing this in the kernel?

Paolo

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