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

[zhenwei pi <pizhenwei@bytedance.com>]

On 6/8/22 07:43, HORIGUCHI NAOYA(堀口 直也) wrote:
> On Tue, Jun 07, 2022 at 02:59:59PM -0700, Andrew Morton wrote:
>> On Tue, 7 Jun 2022 14:36:00 +0200 David Hildenbrand <david@redhat.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, the impact of the bug is limited.
> 
>>
>> 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?
> 
> mf_mutex is to ensure that only one error handling thread can handle
> the pfn at one time, but set_mce_nospec() is called outside it now.
> So if we want to prevent the race with unmap, both of set_mce_nospec()
> and the new kpte check might need to be done in mf_mutex.
> 
> - Naoya Horiguchi

OK, I'll sent a v2 patch which includes:
- this change gets protected by mf_mutex
- use -EOPNOTSUPP instead of -EPERM

By the way, I assume that the similar trace(provided by Naoya) is not a 
same issue. It seems undissolved huge page with corrupted KPTE. I'm 
trying to fix it ...

-- 
zhenwei pi