linux-kernel - Re: [PATCH v2 0/5] mm/hwpoison: Fix regressions in memory failure handling

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Message-ID: <20250219081037.GAZ7WR_YmRtRvN_LKA@fat_crate.local>
Date: Wed, 19 Feb 2025 09:10:37 +0100
From: Borislav Petkov <bp@...en8.de>
To: "Luck, Tony" <tony.luck@...el.com>
Cc: Shuai Xue <xueshuai@...ux.alibaba.com>,
	"nao.horiguchi@...il.com" <nao.horiguchi@...il.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
	"x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
	"linmiaohe@...wei.com" <linmiaohe@...wei.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"jpoimboe@...nel.org" <jpoimboe@...nel.org>,
	"linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"baolin.wang@...ux.alibaba.com" <baolin.wang@...ux.alibaba.com>,
	"tianruidong@...ux.alibaba.com" <tianruidong@...ux.alibaba.com>
Subject: Re: [PATCH v2 0/5] mm/hwpoison: Fix regressions in memory failure
 handling

On Tue, Feb 18, 2025 at 05:30:19PM +0000, Luck, Tony wrote:
First of all, thanks for explaining - that helps a lot!

> That's how we ended up with *UN*corrected errors tied to *C*MCI.
> 
> Just to add to the confusion, Linux does take an action (in uc_decode_notifier())
> to try to offline the page despite the UC*NA* signature name.

So, AFAIU, hw folks are basically trying to tell us: well, this is
*technically* an uncorrectable error but meh, not really important. We just
met it while fetching some data while scrubbing so who knows whether you'll
consume it or not. Meh...

So why don't we simply do that?

We report the signature but we do not try to offline anything. When we get to
*actually* consume it non-speculatively, *then* we run memory failure and then
we offline the page.

Hmmm?

Would that solve that particular debacle?

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette