On Wed, Mar 10, 2021 at 09:13:24AM -0500, Steven Rostedt wrote: > On Wed, 10 Mar 2021 11:22:48 +0100 > Peter Zijlstra <pet...@infradead.org> wrote: > > > After this FEATURE_NOPL is unused except for required-features for > > x86_64. FEATURE_K8 is only used for PTI and FEATURE_K7 is unused. > > > > AFAICT this negatively affects lots of 32bit (DONTCARE) and 32bit on > > 64bit CPUs (CARELESS) and early AMD (K8) which is from 2003 and almost > > 2 decades old by now (SHRUG). > > > > Everything x86_64 since AMD K10 (2007) was using p6_nops. > > > > And per FEATURE_NOPL being required for x86_64, all those CPUs can use > > p6_nops. So stop caring about NOPs, simplify things and get on with life > > :-) > > Before ripping out all the ideal_nop logic, I wonder if we should just > force the nops you want now (that is, don't change the selected > ideal_nops, just "pretend" that the CPU wants p6_nops), and see if anyone > complains. After a few releases, if there's no complaints, then we can > rip out the ideal_nop logic.
Nah, just rip the entire thing out. You should be happy about deterministic NOPs :-) NOP encoding is not something CPUs should differentiate on, that's just bollocks.
