On Fri, May 22, 2020 at 02:11:15PM +0100, Andrew Cooper wrote: > On 22/05/2020 14:04, Jan Beulich wrote: > > On 22.05.2020 13:11, Roger Pau Monné wrote: > >> That being said, I also don't like the fact that logdity is handled > >> differently between EPT and NPT, as on EPT it's handled as a > >> misconfig while on NPT it's handled as a violation. > > Because, well, there is no concept of misconfig in NPT. > > Indeed. Intel chose to split EPT errors into two - MISCONFIG for > structural errors (not present, or reserved bits set) and VIOLATION for > permissions errors. > > AMD reused the same silicon pagewalker design, so have a single > NPT_FAULT vmexit which behaves much more like a regular pagefault, > encoding structural vs permission errors in the error code.
Maybe I should clarify, I understand that NPT doesn't have such differentiation regarding nested page table faults vs EPT, but I feel like it would be clearer if part of the code could be shared, ie: unify EPT resolve_misconfig and NPT do_recalc into a single function for example that uses the necessary p2m-> helpers for the differing implementations. I think we should be able to tell apart when a NPT page fault is a recalc one by looking at the bits in the EXITINFO1 error field? Anyway, this was just a rant, and it's tangential to the issue at hand, sorry for distracting. Roger.
