IIRC shoot-downs are one of the reasons for using per-cpu PGDs which would be a hard sell to some people. https://forum.osdev.org/viewtopic.php?f=15&t=29661 -Boris On Thu, Mar 14, 2024 at 2:26 PM Ira Weiny wrote: > Edgecombe, Rick P wrote: > > On Thu, 2024-03-14 at 09:27 -0700, Kees Cook wrote: > > > On Mon, Aug 30, 2021 at 04:59:08PM -0700, Rick Edgecombe wrote: > > > > This is a second RFC for the PKS write protected tables concept. > > > > I'm sharing to > > > > show the progress to interested people. I'd also appreciate any > > > > comments, > > > > especially on the direct map page table protection solution (patch > > > > 17). > > > > > > *thread necromancy* > > > > > > Hi, > > > > > > Where does this series stand? I don't think it ever got merged? > > > > There are sort of three components to this: > > 1. Basic PKS support. It was dropped after the main use case was > > rejected (pmem stray write protection). > > This was the main reason it got dropped. > > > 2. Solution for applying direct map permissions efficiently. This > > includes avoiding excessive kernel shootdowns, as well as avoiding > > direct map fragmentation. rppt continued to look at the fragmentation > > part of the problem and ended up arguing that it actually isn't an > > issue [0]. Regardless, the shootdown problem remains for usages like > > PKS tables that allocate so frequently. There is an attempt to address > > both in this series. But given the above, there may be lots of debate > > and opinions. > > 3. The actual protection of the PKS tables (most of this series). It > > got paused when I started to work on CET. In the meantime 1 was > > dropped, and 2 is still open(?). So there is more to work through now, > > then when it was dropped. > > > > If anyone wants to pick it up, it is fine by me. I can help with > > reviews. > > I can help with reviews as well, > Ira > > > > > > > [0] https://lwn.net/Articles/931406/ > > > -- Boris Lukashev Systems Architect Semper Victus