Lightroom is very demanding both in processing and in GPU. Also you need proper screen color calibration to get accurate results. Personally whenever I use the

Lightroom is very demanding both in processing and in GPU. Also you need proper screen color calibration to get accurate results. Personally whenever I use the clone/heal brush Lightroom slows down to almost unusable performance and this is on an i7 + 8GB RAM - I can't imagine running it in a VM. I am sure this is Adobe's fault though cause the same tools in Photoshop perform multiple times faster.