Re: [PATCH v4 0/2] vhost-user reconnect issues during vhost initialization

[Stefan Hajnoczi <stefanha@gmail.com>]

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On Thu, May 28, 2020 at 12:11:17PM +0300, Dima Stepanov wrote:
> Before revising the vhost-user initialization code, we suggest adding
> the sanity checks to be aware of the possible disconnect event and that
> the vhost_dev structure can be in "uninitialized" state.
> 
> The vhost-user-blk daemon is updated with the additional
> "--simulate-disconnect-stage=CASENUM" argument to simulate disconnect during
> VHOST device initialization. For instance:
>   1. $ ./vhost-user-blk -s ./vhost.sock -b test-img.raw --simulate-disconnect-stage=1
>      This command will simulate disconnect in the SET_VRING_CALL handler.
>      In this case the vhost device in QEMU is not set the started field to
>      true.
>   2. $ ./vhost-user-blk -s ./vhost.sock -b test-img.raw --simulate-disconnect-stage=2
>      This command will simulate disconnect in the SET_VRING_NUM handler.
>      In this case the started field is set to true.
> These two cases test different QEMU parts. Also to trigger different code paths
> disconnect should be simulated in two ways:
>   - before any successful initialization
>   - make successful initialization once and try to simulate disconnects
> Also we catch SIGABRT on the migration start if vhost-user daemon disconnected
> during vhost-user set log commands communication.
> 
> Dima Stepanov (2):
>   char-socket: return -1 in case of disconnect during tcp_chr_write
>   vhost-user-blk: delay vhost_user_blk_disconnect
> 
>  chardev/char-socket.c     |  7 ++++---
>  hw/block/vhost-user-blk.c | 38 +++++++++++++++++++++++++++++++++++++-
>  2 files changed, 41 insertions(+), 4 deletions(-)

Hi Dima,
The cover letter mentions ./vhost-user-blk --simulate-disconnect-stage=N
to simulate unexpected disconnects but I don't see that option in
contrib/vhost-user-blk/.

Is there a test case?

Thanks,
Stefan

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