linux-kernel - RE: [PATCH] x86/mce: Set PG_hwpoison page flag to avoid the capture kernel panic

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Message-ID: <SJ1PR11MB6083B06E5B75E429E5143B76FCD39@SJ1PR11MB6083.namprd11.prod.outlook.com>
Date:   Mon, 30 Jan 2023 19:21:15 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     HORIGUCHI NAOYA(堀口　直也) 
        <naoya.horiguchi@....com>
CC:     Borislav Petkov <bp@...en8.de>, "x86@...nel.org" <x86@...nel.org>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "patches@...ts.linux.dev" <patches@...ts.linux.dev>,
        "Li, Zhiquan1" <zhiquan1.li@...el.com>,
        "Song, Youquan" <youquan.song@...el.com>
Subject: RE: [PATCH] x86/mce: Set PG_hwpoison page flag to avoid the capture
 kernel panic

> Although I'm not sure that SGX memory or PMEM pages are expected to be
> included in kdump, but simply setting PageHWPoison does not work for them?
> (Maybe that depends on how kdump handles these types of memory.)

SGX/TDX pages can't be dumped. They are encrypted with no way for kdump to
get the key.

PMEM seems pointless (but I don't know what kdump does here).

> As for HugeTLB, kdump utility should parse the struct page and be aware of
> HugeTLB pages, so maybe setting PageHWPoison on the head page could work.

Or maybe kdump can take not of the PageHWPoison flag on the sub-page of the
huge page? It depends on whether there is any benefit to the dump to include the
not-poisoned parts of a huge page.


> I think that setting PageHWPoison outside hwpoison subsystem is OK here,
> because this is called just before calling panic() so it's expected to not
> conflict with other hwpoison-related code.

Thanks for the review.

-Tony