Starting the virtual machine manager, opened a virtual machine (not relevant but in my case a Fedora workstation), started the machine and clicking on the screen button then moving the mouse pointer onto the virtual machine window. This will bring up a dialog (on top of the virtual machine window)
"virtual machine manager wants to inhibit shortcuts".
After clicking "allow", the mousecursor within virtual machine is no longer visible.
Same if a virtual machine is opened, the actual focus is on client display and the virtual machine will be started by clicking the start icon.
To re-enable the mouse cursor, i have to find one of the top buttons or menu in "blind-mode". Once a button or a menu entry was clicked, the mouse cursor is enabled again.
Outsite of virt-manager, mouse is visible all the time.
Btw, running gnome
Confirming on Gnome on scaled Wayland HiDPI session.
This might be related to fractional scaling under Gnome3 on Wayland. I tested again after a reboot, and disabling fractional scaling, and now the mouse pointer is visible.
Are you running fully updated f27 kernel in the VM? Sounds like this, which should be fixed: https://bugzilla.redhat.com/show_bug.cgi?id=1507931