linux-kernel - Re: [PATCH] mm/memory-failure: don't allow to unpoison hw corrupted page

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Message-Id: <20220607145959.785e54c752f373bcc283732b@linux-foundation.org>
Date:   Tue, 7 Jun 2022 14:59:59 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     HORIGUCHI NAOYA (堀口 直也) 
        <naoya.horiguchi@....com>, zhenwei pi <pizhenwei@...edance.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Tony Luck <tony.luck@...el.com>,
        Wu Fengguang <fengguang.wu@...el.com>
Subject: Re: [PATCH] mm/memory-failure: don't allow to unpoison hw corrupted
 page

On Tue, 7 Jun 2022 14:36:00 +0200 David Hildenbrand <david@...hat.com> wrote:

> On 06.06.22 11:15, HORIGUCHI NAOYA(堀口 直也) wrote:
> >>>    [  917.864266]  <TASK>
> >>>    [  917.864961]  clear_huge_page+0x147/0x270
> >>>    [  917.866236]  hugetlb_fault+0x440/0xad0
> >>>    [  917.867366]  handle_mm_fault+0x270/0x290
> >>>    [  917.868532]  do_user_addr_fault+0x1c3/0x680
> >>>    [  917.869768]  exc_page_fault+0x6c/0x160
> >>>    [  917.870912]  ? asm_exc_page_fault+0x8/0x30
> >>>    [  917.872082]  asm_exc_page_fault+0x1e/0x30
> >>>    [  917.873220] RIP: 0033:0x7f2aeb8ba367
> >>>
> >>> I don't think of a workaround for this now ...
> >>>
> >>
> >> Could you please tell me how to reproduce this issue?
> > 
> > You are familiar with qemu-monitor-command, so the following procedure
> > should work for you:
> > 
> >   - run a process using hugepages on your VM,
> >   - check the guest physical address of the hugepage (page-types.c is helpful for this),
> >   - inject a MCE with virsh qemu-monitor-command on the guest physical address, then
> >   - unpoison the injected physical address.
> 
> That's triggered via debugfs / HWPOISON_INJECT, right?
> 
> That's a DEBUG_KERNEL option, so I'm not 100% sure if we really want to
> cc stable.

Sure, it's hardly a must-have.  But let's also take the patch
complexity&risk into account.  This is one dang simple patch.

Or is it.  Should these things be happening outside mf_mutex?  What the
heck is the role of mf_mutex anyway?