[PATCH v5 00/25] context_tracking,x86: Defer some IPIs until a user->kernel transition

[Peter Zijlstra]

On Wed, Apr 30, 2025 at 11:07:35AM -0700, Dave Hansen wrote:

> Both AMD and Intel have hardware to do it. ARM CPUs do it too, I think.
> You can go buy the Intel hardware off the shelf today.

To be fair, the Intel RAR thing is pretty horrific :-( Definitely
sub-par compared to the AMD and ARM things.

Furthermore, the paper states it is a uarch feature for SPR with no
guarantee future uarchs will get it (and to be fair, I'd prefer it if
they didn't).

Furthermore, I suspect it will actually be slower than IPIs for anything
with more than 64 logical CPUs due to reduced parallelism.