On Tue, Dec 07, 2021, Lai Jiangshan wrote: > From: Lai Jiangshan <laijs@xxxxxxxxxxxxxxxxx> > > In same cases, it doesn't need to get rflags for SMAP checks. > > For example: it is user mode access, it could have contained other > permission fault, SMAP is not enabled, it is implicit supervisor > access, or it is nested TDP pagetable. I don't disagree that reading RFLAGS is silly and _may_ have worse performance, but I'd prefer any change have actual numbers to justify that it's an improvement or at least a wash / in the noise. Too much of the MMU code (and KVM in general) has optimizations like this that have bitrotted horribly over the years. And in many/most cases, the original commit didn't provide performance numbers, so it's not even clear that the "optimizations" were _ever_ a net win.
