I recently installed RHEL 7 as a Hyper-V guest vm.  Unlike other VMs i couldn’t adjust the screen resolution and 800x600 got very boring, very quickly.  A quick google search found this blog by Netometer, which showed how to set it using the command line.  1024x768 was ok, but it didn’t match the resolution of my laptop.  So i set resolution to 3000x2000 and rebooted.  Epic fail, a message in the start up stated that there was an invalid screen resolution and reverted back to 800X600.  I tried again stepping up through the resolutions my laptop supported and eventually settled at 1920x1080.  The code i eventually used it below

sudo grubby –update-kernel=ALL –args="video=hyperv_fb:1920×1080"

sudo reboot

there may be  a better way to do this, if i find it I’ll update this post