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Re: [libvirt] [PATCH] bhyve: implement domainShutdown



On Tue, Mar 29, 2016 at 10:52:09AM -0400, Laine Stump wrote:
> On 03/29/2016 08:24 AM, Daniel P. Berrange wrote:
> >On Mon, Mar 28, 2016 at 10:27:18AM +0300, Roman Bogorodskiy wrote:
> >>Bhyve supports ACPI shutdown by issuing SIGTERM signal to the bhyve
> >>process. Add the bhyveDomainShutdown() function and
> >>virBhyveProcessShutdown() helper function that just sends SIGTERM to
> >>VM's bhyve process. If a guest supports ACPI shutdown then process
> >>will be terminated and this event will be noticed by the bhyve monitor
> >>code that will handle setting proper status and clean up VM's resources.
> >>
> >>Also, remove a warning in domainDestroy in case if
> >>virProcessKillPainfully() returns 1, meaning that it killed process
> >>using SIGKILL. This behavior should be expected when using 'destroy'.
> >Hmm, so destroy is supposed to be equivalent to physically removing
> >the power plug.  The existing code is calling virProcessShutdownPainfully
> >which starts by sending SIGTERM and then switches to SIGKILL.  So this
> >means that your virDomainDestroy implementation is mistakenly trying todo
> >a graceful shutdown initially and then switching to hard shutdown after a
> >bit of a delay.
> 
> For context - the qemu driver does this for destroy as well. I think at
> least one of the reasons is to allow the qemu process to flush the buffers
> for the disk image files. I recall this was causing some amount of pain for
> ovirt (or maybe someone else, I forget)

Yep it is different in QEMU - SIGTERM doesn't trigger any guest OS ACPI
event with QEMU - it merely lets QEMU gracefully close the block
layer functions and flush I/O.

> >Has bhyve always used SIGTERM to trigger ACPI shutdown, or is this a
> >recent addition ?  I would tend to suggest we need to go straight to
> >SIGKILL for virDomainDestroy to avoid doing ACPI shutdown when we don't
> >want it.
> >
> >It is kind of a shame they used SIGTERM for triggering ACPI imho but
> >oh well.
> 
> Yes, it means there is no way to implement a "clean power off" (which would
> give bhyve the chance to clean up some critical things before pulling the
> plug).

Yeah, exactly, it is desirable to be able to do a immediate forced shutdown
of guest OS while still letting the host process exit cleanly.


Regards,
Daniel
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