On Sun, Nov 13, 2022 at 2:35 AM Mike Rapoport <rppt@xxxxxxxxxx> wrote: > > On Wed, Nov 09, 2022 at 05:04:25PM +0000, Edgecombe, Rick P wrote: > > On Wed, 2022-11-09 at 13:17 +0200, Mike Rapoport wrote: > > > On Tue, Nov 08, 2022 at 04:51:12PM +0000, Edgecombe, Rick P wrote: > > > > > How the caching of large pages in vmalloc can be made useful for use > > > cases like secretmem and PKS? > > > > This part is easy I think. If we had an unmapped page allocator it > > could just feed this. > > The unmapped page allocator could be used by anything that needs > non-default permissions in the direct map and knows how to map the pages > elsewhere. E.g it would have been a oneliner to switch x86::module_alloc() > to use unmapped allocations. But ... > > > Do you have any idea when you might pick up that stuff again? > > ... unfortunately I don't see it happening anytime soon. > > > To answer my own question, I think a good first step would be to make > > the interface also work for non-text_poke() so it could really be cross > > arch, then use it for everything except modules. The benefit to the > > other arch's at that point is centralized handling of loading text. > > My concern is that the proposed execmem_alloc() cannot be used for > centralized handling of loading text. I'm not familiar enough with > modules/ftrace/kprobes/BPF to clearly identify the potential caveats, but > my gut feeling is that the proposed execmem_alloc() won't be an improvement > but rather a hindrance for moving to centralized handling of loading text. I don't follow why this could ever be a hindrance. Luis is very excited about this, and I am very sure it works for ftrace, kprobe, and BPF. If there is a better API, it shouldn't be too hard to do the migration. See the example in 3/5 of the set, where we move x86 BPF jit AND BPF dispatcher from bpf_prog_pack to execmem_alloc(): 5 files changed, 21 insertions(+), 201 deletions(-) It is not a one liner, but it is definitely very easy. > > It feels to me that a lot of ground work is needed to get to the point > where we can use centralized handling of loading text. Could you please be more specific on what is needed? Thanks, Song
