[Libguestfs] [PATCH 1/1] windows: delay installation of qemu-ga MSI

[Tomáš Golembiovský]

On Tue, Mar 03, 2020 at 01:37:24PM +0000, Daniel P. Berrangé wrote:
> On Tue, Mar 03, 2020 at 02:27:46PM +0100, Tomáš Golembiovský wrote:
> > On Mon, Mar 02, 2020 at 11:35:29AM +0000, Daniel P. Berrangé wrote:
> > > On Mon, Mar 02, 2020 at 12:26:00PM +0100, Tomáš Golembiovský wrote:
> > > > Instead of running firstboot script during early boot schedule a task
> > > > delayed for 1-2 minute.
> > > 
> > > IIUC, you picked 119 seconds, so effectively 2 minutes. IOW, s/1-2/2/
> > > 
> > 
> > Well, the time is rounded down to minutes. It cannot be scheduled with
> > precision in seconds. So when scheduling in 00:00:00 it will be set to
> > 00:01:00. But now that I look at it it should be 120 and not 119. That
> > way it will always be 2 minutes. I am not sure what math error did I do
> > when I wrote it originaly.
> > 
> > 
> > > > During the first boot, after virt-v2v conversion, Windows installs the
> > > > drivers injected by virit-v2v. When this installation is finished
> > > 
> > > s/virit/virt/
> > > 
> > > > Windows enforces some kind of internal reboot. This unfortunately
> > > > terminates any running firstboot scritps thus killing the installation
> > > 
> > > s/scritpts/scripts/
> > > 
> > 
> > Thanks for spotting the typos.
> > 
> > > > of qemu-ga MSI.
> > > 
> > > IIUC, the expectation is that the Windows installation of the
> > > drivers will be completed *before* this 2 minute delay occurs.
> > > Windows will then reboot, and the delayed GA job will be run
> > > after this reboot ?
> > 
> > Correct.
> > 
> > > 
> > > The key question is how confident are we that the 2 minute
> > > delay is sufficient ?  Is there chance of still hitting the
> > > problem if doing v2v on slow (ie HDD, not SSD) storage
> > > for example ?
> > 
> > This is a best effort. What you're describing can happen and the user
> > will be screwed. But bear in mind that as it is now it is virtualy never
> > working. You cannot set the delay too long either. If the user starts
> > doing something once the VM boots you don't want to restart the VM (once
> > MSI is installed) under the user's hands.
> > 
> > I am currently investigating how could we use PowerShell features to
> > introduce some waiting mechanism (e.g. for the serial device) to handle
> > this better. But that will take some time.
> 
> Ok, understood. Can you expand the commit message with some of this
> info to make it clear this isn't a real fix, it is just a mitigation
> with caveats about possible failure in slow VMs.

Updated in v3. Let me know if you think I omitted something.

    Tomas

> 
> 
> Regards,
> Daniel
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-- 
Tomáš Golembiovský <tgolembi at redhat.com>