> > > >gfn_to_page is the interface for mapping guest pages inside KVM, > > > >and you're bypassing it for IMO no good reason (i doubt there's any > > > >performance improvement by skipping the translation). > > > > > > He isn't skipping it - he's using gfn_to_hva() to derive ptep_user, > > > which is equivalent. > > > > Well, he is removing the second translation. So that is skipped. > > hva->gpa translation is not supposed to be changed by kvm. > > > > The motivation isn't performance, it's to ensure that cmpxchg_gpte() > > > operates on the same address as we read it from. > > > > OK, my objection is direct get_user_pages_fast usage. Please pass gfn to > > gfn_to_page. > > We do get_user() in read_gpte(). That is equivalent to > get_user_pages(). So we already broke that layer of abstraction. At first, I broke hva_to_pfn() into two functions: hva_to_page hva_to_pfn and used the former to get the page. But after making that patch, I thought it might be a bit extra to do such things in the function which is doing low level page manipulations like kmapping. Actually, we are already assuming that the page returned by gfn_to_page is always a usual page which contains gptes without extra checks. Which way do you like the best? Takuya -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
