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Message-ID: <68a4a96b-9c66-6509-e75d-b1bea6cd55d1@redhat.com>
Date:   Tue, 24 May 2022 20:59:09 +0200
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Subject: Re: [PATCH 0/3] recover hardware corrupted page by virtio balloon
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To:     zhenwei pi <pizhenwei@bytedance.com>, akpm@linux-foundation.org,
        naoya.horiguchi@nec.com, mst@redhat.com
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        jasowang@redhat.com, virtualization@lists.linux-foundation.org,
        pbonzini@redhat.com, peterx@redhat.com, qemu-devel@nongnu.org
References: <20220520070648.1794132-1-pizhenwei@bytedance.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
In-Reply-To: <20220520070648.1794132-1-pizhenwei@bytedance.com>
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On 20.05.22 09:06, zhenwei pi wrote:
> Hi,
> 
> I'm trying to recover hardware corrupted page by virtio balloon, the
> workflow of this feature like this:
> 
> Guest              5.MF -> 6.RVQ FE    10.Unpoison page
>                     /           \            /
> -------------------+-------------+----------+-----------
>                    |             |          |
>                 4.MCE        7.RVQ BE   9.RVQ Event
>  QEMU             /               \       /
>              3.SIGBUS              8.Remap
>                 /
> ----------------+------------------------------------
>                 |
>             +--2.MF
>  Host       /
>        1.HW error
> 
> 1, HardWare page error occurs randomly.
> 2, host side handles corrupted page by Memory Failure mechanism, sends
>    SIGBUS to the user process if early-kill is enabled.
> 3, QEMU handles SIGBUS, if the address belongs to guest RAM, then:
> 4, QEMU tries to inject MCE into guest.
> 5, guest handles memory failure again.
> 
> 1-5 is already supported for a long time, the next steps are supported
> in this patch(also related driver patch):
> 
> 6, guest balloon driver gets noticed of the corrupted PFN, and sends
>    request to host side by Recover VQ FrontEnd.
> 7, QEMU handles request from Recover VQ BackEnd, then:
> 8, QEMU remaps the corrupted HVA fo fix the memory failure, then:
> 9, QEMU acks the guest side the result by Recover VQ.
> 10, guest unpoisons the page if the corrupted page gets recoverd
>     successfully.
> 
> Test:
> This patch set can be tested with QEMU(also in developing):
> https://github.com/pizhenwei/qemu/tree/balloon-recover
> 
> Emulate MCE by QEMU(guest RAM normal page only, hugepage is not supported):
> virsh qemu-monitor-command vm --hmp mce 0 9 0xbd000000000000c0 0xd 0x61646678 0x8c
> 
> The guest works fine(on Intel Platinum 8260):
>  mce: [Hardware Error]: Machine check events logged
>  Memory failure: 0x61646: recovery action for dirty LRU page: Recovered
>  virtio_balloon virtio5: recovered pfn 0x61646
>  Unpoison: Unpoisoned page 0x61646 by virtio-balloon
>  MCE: Killing stress:24502 due to hardware memory corruption fault at 7f5be2e5a010
> 
> And the 'HardwareCorrupted' in /proc/meminfo also shows 0 kB.
> 
> About the protocol of virtio balloon recover VQ, it's undefined and in
> developing currently:
> - 'struct virtio_balloon_recover' defines the structure which is used to
>   exchange message between guest and host.
> - '__le32 corrupted_pages' in struct virtio_balloon_config is used in the next
>   step:
>   1, a VM uses RAM of 2M huge page, once a MCE occurs, the 2M becomes
>      unaccessible. Reporting 512 * 4K 'corrupted_pages' to the guest, the guest
>      has a chance to isolate the 512 pages ahead of time.
> 
>   2, after migrating to another host, the corrupted pages are actually recovered,
>      once the guest gets the 'corrupted_pages' with 0, then the guest could
>      unpoison all the poisoned pages which are recorded in the balloon driver.
> 

Hi,

I'm still on vacation this week, I'll try to have a look when I'm back
(and flushed out my overflowing inbox :D).


-- 
Thanks,

David / dhildenb