Known Issues
SVM error
Cycles: out of SVM stack space
This issue is not common, but is something can come up in some occasions. We cannot provide information in which those instances are because the SVM stack (Shared Virtual Memory) uses a non-deterministic approach to calculate "items" in any given shader. These "Items" are not known, and are not nodes or output values. So this makes it hard for us to address this limit as we cannot be sure what is classed as an "item" and how that is taken into account by the SVM.
The SVM limit is 256 items, and this is a hard limit built into Blender. We have reached out to Blender.org for more information about this and all they are able to provide is that the SVM limit cannot be increased as this has huge negative impacts on the management of VRAM and system RAM (Depending on what compute device you use to render, either GPU or CPU). This is an unfortunate case of "It may happen, it may not" and when/if you do receive this error, we cannot provide a fix for it.
If you get this error, this will usually happen after you make a change to the material. We advise that you undo said change and your material will return.