[PATCH 0/3] recover hardware corrupted page by virtio balloon

zhenwei pi
Fri, 20 May 2022 07:06:45 -0000

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.

zhenwei pi (3):
  memory-failure: Introduce memory failure notifier
  mm/memory-failure.c: support reset PTE during unpoison
  virtio_balloon: Introduce memory recover

 drivers/virtio/virtio_balloon.c     | 243 ++++++++++++++++++++++++++++
 include/linux/mm.h                  |   4 +-
 include/uapi/linux/virtio_balloon.h |  16 ++
 mm/hwpoison-inject.c                |   2 +-
 mm/memory-failure.c                 |  59 ++++++-
 5 files changed, 315 insertions(+), 9 deletions(-)

--
2.20.1