Re: [PATCH v2 00/13] Dynamic Kernel Stacks

[Zach O'Keefe]

On Mon, Apr 27, 2026 at 9:22 AM Dave Hansen <dave.hansen@xxxxxxxxx> wrote:
>
> On 4/25/26 02:19, H. Peter Anvin wrote:
> > It is worth noting that this was one of the VERY early design decisions that
> > has shaped Linux from the beginning:
> >
> > - No swapping of kernel memory
> > - Kernel stacks are statically allocated
> ...
>
> One other bit to add here: In the past, kernel faults on kernel memory
> have been allowed, like to populate vmalloc() page table entries into
> the parts of the page tables that are not shared across processes. Even
> *that* turned out to be too much of a pain even though it didn't involve
> allocation, and the kernel has been moving away from that.
>

Dave,

Necroing this thread, as the potential aggregate savings continue to
stand out for us on the datacenter side (whereas David is motivated
separately, from the consumer device side).

I certainly empathize with your position, and hesitation to give up
such a nice simplification just to invite new headaches.

However, I'd still like to work with you to understand what feasible
path forward you see, hoping you can proactively steer us away from
some of the bigger headaches.

I think we are fine being forward-looking, and only supporting this
for FRED (which is on our doorstep). That said, understanding the
issues you foresee with the IST approach would still be valuable, as
it might save us internal trouble should we choose to carry it
temporarily to bridge the gap with FRED.

Overall, are there any particular painpoints you'd like to see flushed
out, first? How would you like to proceed? Would explicitly marking
this as an experimental config, in the interim, be more attractive?

Thanks, and I appreciate any help or guidance here.

Best,
Zach