linux-kernel - Re: [PATCH] mm/hwpoison: avoid speculation access after soft/hard offline

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Message-ID: <871q4hzlf0.fsf@linux.intel.com>
Date: Thu, 27 Jun 2024 22:27:47 -0700
From: Andi Kleen <ak@...ux.intel.com>
To: Ruidong Tian <tianruidong@...ux.alibaba.com>
Cc: linux-kernel@...r.kernel.org,  linux-mm@...ck.org,
  akpm@...ux-foundation.org,  nao.horiguchi@...il.com,
  linmiaohe@...wei.com,  tianruidong@...baba.linux.com,
  xueshuai@...ux.alibaba.com
Subject: Re: [PATCH] mm/hwpoison: avoid speculation access after soft/hard
 offline

Ruidong Tian <tianruidong@...ux.alibaba.com> writes:

> Page that offlined can report CE/UE event due to speculation access.
> Delete kernel 1:1 linner mapping after soft/hard offline to avoid it.

But that will split the large pages for the direct mapping, costing you
every time there is TLB pressure. You can probably do the math, with
enough uptime and a reasonable error rate aand this patch there might be
not even be 2MB pages left at some point. Cheaper to just ignore them,
since they shouldn't cause any other problems.

-Andi