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| author | Paolo Bonzini <pbonzini@redhat.com> | 2014-06-05 14:53:59 +0200 |
|---|---|---|
| committer | Stefan Hajnoczi <stefanha@redhat.com> | 2014-06-23 16:36:13 +0800 |
| commit | 2bd3bce8efebe86b031beab5c0e3b9bbaec0b502 (patch) | |
| tree | f0c9c33850b6e351afe75d315611bd2047cf6011 /docs | |
| parent | 74892d2468b9f0c56b915ce94848d6f7fac39740 (diff) | |
| download | qemu-2bd3bce8efebe86b031beab5c0e3b9bbaec0b502.tar.gz | |
block: asynchronously stop the VM on I/O errors
With virtio-blk dataplane, I/O errors might occur while QEMU is
not in the main I/O thread. However, it's invalid to call vm_stop
when we're neither in a VCPU thread nor in the main I/O thread,
even if we were to take the iothread mutex around it.
To avoid this problem, we can raise a request to the main I/O thread,
similar to what QEMU does when vm_stop is called from a CPU thread.
We know that bdrv_error_action is called from an AIO callback, and
the moment at which the callback will fire is not well-defined; it
depends on the moment at which the disk or OS finishes the operation,
which can happen at any time. Note that QEMU is certainly not in a CPU
thread and we do not need to call cpu_stop_current() like vm_stop() does.
However, we need to ensure that any action taken by management will
result in correct detection of the error _and_ a running VM. In particular:
- the event must be raised after the iostatus has been set, so that
"info block" will return an iostatus that matches the event.
- the VM must be stopped after the iostatus has been set, so that
"info block" will return an iostatus that matches the runstate.
The ordering between the STOP and BLOCK_IO_ERROR events is preserved;
BLOCK_IO_ERROR is documented to come first.
This makes bdrv_error_action() thread safe (assuming QMP events are,
which is attacked by a separate series).
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/qmp/qmp-events.txt | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/docs/qmp/qmp-events.txt b/docs/qmp/qmp-events.txt index 019db53ec8..22fea580a9 100644 --- a/docs/qmp/qmp-events.txt +++ b/docs/qmp/qmp-events.txt @@ -62,7 +62,7 @@ Data: - "action": action that has been taken, it's one of the following (json-string): "ignore": error has been ignored "report": error has been reported to the device - "stop": error caused VM to be stopped + "stop": the VM is going to stop because of the error Example: |