On Mon, Dec 04, 2017 at 02:22:54PM -0800, Andy Lutomirski wrote: > > +static inline void invalidate_pcid_other(void) > > +{ > > + /* > > + * With global pages, all of the shared kenel page tables > > + * are set as _PAGE_GLOBAL. We have no shared nonglobals > > + * and nothing to do here. > > + */ > > + if (!static_cpu_has_bug(X86_BUG_CPU_SECURE_MODE_KPTI)) > > + return; > > I think I'd be more comfortable if this check were in the caller, not > here. Shouldn't a function called invalidate_pcid_other() do what the > name says?
Yeah, you're probably right. The thing is course that we only ever need that operation for kpti (as of now). But me renaming this stuff made this problem :/ > > + this_cpu_write(cpu_tlbstate.invalidate_other, true); > > Why do we need this extra variable instead of just looping over all > other ASIDs and invalidating them? It would be something like: > > for (i = 1; i < TLB_NR_DYN_ASIDS; i++) { > if (i != this_cpu_read(cpu_tlbstate.loaded_mm_asid)) > this_cpu_write(cpu_tlbstate.ctxs[i].ctx_id, 0); > } > > modulo epic whitespace damage and possible typos. I think the point is that we can do many invalidate_other's before we ever do a switch_mm(). The above would be more expensive. Not sure it would matter in practise though. > > static inline void __flush_tlb_one(unsigned long addr) > > { > > count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ONE); > > __flush_tlb_single(addr); > > + /* > > + * Invalidate other address spaces inaccessible to single-page > > + * invalidation: > > + */ > > Ugh. If I'm reading this right, __flush_tlb_single() means "flush one > user address" and __flush_tlb_one() means "flush one kernel address". That would make sense, woulnd't it? :-) But afaict the __flush_tlb_one() user in tlb_uv.c is in fact for userspace and should be __flush_tlb_single(). Andrew, Mike, can either of you shed light on what exactly you need invalidated there? > That's, um, not exactly obvious. Could this be at least commented > better? As is __flush_tlb_single() does user and __flush_tlb_one() does user+kernel.