FWIW, I'm also hit by this on a HP Spectre X360 with a Vega M configuration
(thought it's notable as the other reports seem to only come from Dell
machines?). Disabling the Vega M by doing `echo 1 >
/sys/bus/pci//devices/0000:01:00.0/remove` hasn't changed a thing (Checked by
lspci first, that is the right device) and booting with `acpi=off` causes my
touchpad and the thunderbolt controller to not function at all (apparently?),
so there's that.

Am using a RX470 in a Razer Core X, which works flawlessly on Windows. But I
guess the Vega M does the trick on Linux for now, thanks for the great work on
amdgpu and Mesa :)