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SubjectRe: [PATCH] mm/memory-failure: don't allow to unpoison hw corrupted page
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On 07.06.22 23:59, 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, 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?

For example, I'm not even sure if we're allowed to use virt_to_kpte()
out of random context at all.

If we have a PMD direct map, why should it be okay to use virt_to_kpte()?

Maybe I am just wrong, I asked that question on the next patch version
as well.

--
Thanks,

David / dhildenb

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