USB devices unusable post update to 5.2

[TitelSin]

Hello I've been trying to get this going again for a long time now, but I can't seem to get it going, so I'm posting here.

I have an offline Windows XP VM that I passthrough a USB sensor we use for measurements to. The old physical machine that was used for these measurements has long died and up until the last update everything worked out great. Since we upgraded VirtualBox to 5.2.0 r118431 (Qt5.6.3) any time the sensor is in use the host CPU spikes to 100% and makes the VM very slow and unresponsive. Clicks get accepted after multiple seconds, stuff like that.

The VM itself shows very little CPU usage, 3-5%, but the host ist maxed out. From what I've googled a lot of people are having similar issues of late.

Things I've tried so far is giving the VM more cores, more RAM, changed through all the acceleration settings, changed the chipset(but VM wouldn't boot anymore) so changed that back. I'm pretty much at the end of what I can try on my end to get the VM running smoothly again. Also updated the guest additions first thing when I noticed the problem.

The host machine has the following specs:
Intel Core i7-4980HQ
16GB of RAM
Integrated HD graphics
MacOS Sierra 10.12.6 (16G1314)

The VM was originally running one core and 256mb of RAM without any issue. It how has 2 cores and 512gb of RAM and is unusable. USB is running in 1.1 mode, same as before update.

Anything else I should be looking at or trying?
EDIT: Added exact version numbers.

[socratis]

Since we upgraded VirtualBox to 5.2.0 r118431 (Qt5.6.3)

Have you tried to downgrade to whatever version you were using before that?

USB sensor ... USB is running in 1.1 mode

There were way too few USB devices that were using USB1. Are you sure that yours is such a device? What happens if you switch the controller in the VM settings to USB2?

a lot of people are having similar issues of late

With your device? If not, please clarify.

[TitelSin]

I updated to the latest version I could download, Version 5.2.8 r121009 (Qt5.6.3) , I installed the guest additions from this version and this seems to have solved the main issue, but not quite satisfactory. Now the VM load on the host is in the 70s-80% range, the VM itself is much more responsive than before.

I still think this CPU usage is quite high considering that the VM is almost idling while reading from the usb sensor.

And to respond to your question socratis, since the beginning the USB sensor was running in 1.1 mode. This is a light sensor that effectively reads one value, light intensity and the software plots a graph based on how that intensity changes. Based on that graph we have our measurements. I don't think this ever needed high speed USB 2.0. The original, older version of this sensor came with a COM1 connector.

When I was googling my problem I notice a lot o people having similar behaviour with either XP or Windows 7 guests, where the guests were basically idling but the host was under heavy load post 5.2 update. My guess right now is that this might be to meltdown/specter mitigations being more aggressive than in the past.

For our usage right now, the load on the host has been lowered, making both machines usable again. It would be good if it was better but I'm ok with it.

Also worth asking, now that the guest has the latest guest additions installed, will it start/work if I try to start it with an older version of VirtualBox, say 5.0 or 5.1?

[socratis]

When you upgrade VirtualBox it's a good idea to update the Guest Additions (GAs). But the USB and the GAs have nothing to do with each other.

Also, downgrading your VirtualBox and the GAs shouldn't be a big deal just to try it out and see if that's actually the problem.