14 Jul
2022
14 Jul
'22
5:38 p.m.
On Thu, Jul 14, 2022 at 07:03:32PM +0200, Peter Zijlstra wrote:
On Thu, Jul 14, 2022 at 09:01:06AM -0700, Josh Poimboeuf wrote:
Yeah this; if the user asks for IBRS, we should give him IBRS. I hate the 'I know better, let me change that for you' mentality.
eIBRS CPUs don't even have legacy IBRS so I don't see how this is even possible.
You can still WRMSR a lot on them. Might not make sense but it 'works'.
Even in Intel documentation, eIBRS is often referred to as IBRS. It wouldn't be surprising for a user to consider spectre_v2=ibrs to mean "use eIBRS".
I'm pretty sure there's nobody out there that wants spectre_v2=ibrs to mean "make it slower and possibly less secure because it's being used contrary to the spec".
--
Josh