On Tue, 15 May 2018, Boaz Harrosh wrote: > > I don't think page tables work the way you think they work. > > > > + err = vm_insert_pfn_prot(zt->vma, zt_addr, pfn, prot); > > > > That doesn't just insert it into the local CPU's page table. Any CPU > > which directly accesses or even prefetches that address will also get > > the translation into its cache. > > > > Yes I know, but that is exactly the point of this flag. I know that this > address is only ever accessed from a single core. Because it is an mmap (vma) > of an O_TMPFILE-exclusive file created in a core-pinned thread and I allow > only that thread any kind of access to this vma. Both the filehandle and the > mmaped pointer are kept on the thread stack and have no access from outside. > > So the all point of this flag is the kernel driver telling mm that this > address is enforced to only be accessed from one core-pinned thread. But there are no provisions for probhiting accesses from other cores? This means that a casual accidental write from a thread executing on another core can lead to arbitrary memory corruption because the cache flushing has been bypassed.
