USB 3.0 ports not working (16.04)

I bought an Asus X550VX laptop a few weeks ago and installed Ubuntu 16.04 alongside Windows 10 on it. For a week or so everything worked fine, until one of the USB 3.0 ports stopped working. Soon after that, the other port stopped working too. The one USB 2 port still works fine. When I connect my phone to a USB 3 port it charges, but Ubuntu doesn't recognize that a device is connected. My wireless mouse doesn't work either on those ports.

I've googled around but nothing seems to help. I've updated my bios and added a "pci=nomsi" line to grub file. Any other suggestions?

This ought to do it:

1. sudo gedit /etc/default/grub
2. Find this line: GRUB_CMDLINE_LINUX=""
3. Change it to GRUB_CMDLINE_LINUX="iommu=soft"
4. Save
5. Run sudo update-grub
6. Reboot