On Wed, 2018-12-12 at 06:30 +0000, Nadav Amit wrote: > > On Dec 11, 2018, at 4:03 PM, Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx> > > wrote: > > > > This adds a more efficient x86 architecture specific implementation of > > arch_vunmap, that can free any type of special permission memory with only 1 > > TLB > > flush. > > > > In order to enable this, _set_pages_p and _set_pages_np are made non-static > > and > > renamed set_pages_p_noflush and set_pages_np_noflush to better communicate > > their different (non-flushing) behavior from the rest of the set_pages_* > > functions. > > > > The method for doing this with only 1 TLB flush was suggested by Andy > > Lutomirski. > > > > [snip] > > > + /* > > + * If the vm being freed has security sensitive capabilities such as > > + * executable we need to make sure there is no W window on the directmap > > + * before removing the X in the TLB. So we set not present first so we > > + * can flush without any other CPU picking up the mapping. Then we reset > > + * RW+P without a flush, since NP prevented it from being cached by > > + * other cpus. > > + */ > > + set_area_direct_np(area); > > + vm_unmap_aliases(); > > Does vm_unmap_aliases() flush in the TLB the direct mapping range as well? I > can only find the flush of the vmalloc range. Hmmm. It should usually (I tested), but now I wonder if there are cases where it doesn't and it could depend on architecture as well. I'll have to trace through this to verify, thanks. Rick
