linux-kernel - Re: [PATCH v6 1/1] mm/memory-failure: disable unpoison once hw error happens

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Date:   Wed, 15 Jun 2022 22:58:14 +0000
From:   HORIGUCHI NAOYA(堀口　直也) 
        <naoya.horiguchi@....com>
To:     Andrew Morton <akpm@...ux-foundation.org>
CC:     zhenwei pi <pizhenwei@...edance.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "david@...hat.com" <david@...hat.com>,
        "linmiaohe@...wei.com" <linmiaohe@...wei.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Oscar Salvador <osalvador@...e.de>
Subject: Re: [PATCH v6 1/1] mm/memory-failure: disable unpoison once hw error
 happens

On Wed, Jun 15, 2022 at 01:49:33PM -0700, Andrew Morton wrote:
> On Wed, 15 Jun 2022 10:34:06 +0000 HORIGUCHI NAOYA(堀口　直也) <naoya.horiguchi@....com> wrote:
> 
> > On Wed, Jun 15, 2022 at 05:32:09PM +0800, zhenwei pi wrote:
> > > Currently unpoison_memory(unsigned long pfn) is designed for soft
> > > poison(hwpoison-inject) only. Since 17fae1294ad9d, the KPTE gets
> > > cleared on a x86 platform once hardware memory corrupts.
> > > 
> > > Unpoisoning a hardware corrupted page puts page back buddy only,
> > > the kernel has a chance to access the page with *NOT PRESENT* KPTE.
> > > This leads BUG during accessing on the corrupted KPTE.
> > > 
> > > Suggested by David&Naoya, disable unpoison mechanism when a real HW error
> > > happens to avoid BUG like this:
> > > 
> >
> > ...
> >
> > > 
> > > Fixes: 847ce401df392 ("HWPOISON: Add unpoisoning support")
> > > Fixes: 17fae1294ad9d ("x86/{mce,mm}: Unmap the entire page if the whole page is affected and poisoned")
> > > Cc: Naoya Horiguchi <naoya.horiguchi@....com>
> > > Cc: David Hildenbrand <david@...hat.com>
> > > Cc: Oscar Salvador <osalvador@...e.de>
> > > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > > Acked-by: David Hildenbrand <david@...hat.com>
> > > Signed-off-by: zhenwei pi <pizhenwei@...edance.com>
> > 
> > Thank you very much.
> > 
> > Acked-by: Naoya Horiguchi <naoya.horiguchi@....com>
> 
> I added cc:stable to this.  But the dual Fixes: are going to confuse
> people regarding which kernel versions need the fix.  Can we be more
> specific?

OK.  This bug was visible since 17fae1294ad9d (merged in v5.8 time period),
so marking "v5.8+" on "Cc: stable" line would be helpful.

- Naoya Horiguchi