Andrew points out that 'x86/shadow: suppress "fast fault path" optimization without reserved bits' assumes firm knowledge of the physical machine's address width. When we run virtualized ourselves, we can't reasonably assume that we do, the more that the property may change as we may get migrated.
Since we want to further refine this logic anyway, I thought I'd also include the other change that I've previously mentioned, at least for consideration whether to take for 4.15. This reduces the performance impact (albeit perhaps only for very large or exotic guests) that the earlier patch has. 1: suppress "fast fault path" optimization when running virtualized 2: encode full GFN in magic MMIO entries Jan