Re: [PATCH] vhost-scsi: Take configfs group dependency during VHOST_SCSI_SET_ENDPOINT

[Paolo Bonzini <pbonzini@redhat.com>]

Il 09/10/2014 06:14, Nicholas A. Bellinger ha scritto:
> AFAICT from qemu code, the ioctl VHOST_SCSI_CLEAR_ENDPOINT is always
> called during shutdown in order to release the endpoint and drop this
> new configfs dependency.

As far as I can see, the only path leading to the ioctl is
vhost_scsi_set_status->vhost_scsi_stop.  That only happens if the guest
driver resets the device upon shutdown, or via vhost_scsi_unrealize as
you pointed out.  But unrealize() is only called when a device is
hot-unplugged.

It does not happen if you close QEMU with SIGTERM, ctrl-c, or with the
"quit" command, because no attempt is done to bring down the VM data
structures (or free memory, or close file descriptors) in case of a
fatal exit.  The kernel should do that for us.

Besides that...

> The question is, what happens when qemu crashes..?  Is there currently
> an assurance that VHOST_SCSI_CLEAR_ENDPOINT is called via the normal
> VirtioDeviceClass->unrealize() when qemu exits abnormally..?

... of course nothing is called if you SIGKILL QEMU.

Paolo