On 08/09/2021 11:43, Jan Beulich wrote: > On 07.09.2021 18:19, Andrew Cooper wrote: >> The opencoded legacy Memory Disambiguation logic in init_amd() neglected >> Fam19h for the Zen3 microarchitecture. In practice, all Zen2 based system >> have the architectural MSR_SPEC_CTRL and the SSBD bit within it. > Don't you mean Zen3 in the 2nd sentence? Otherwise there's a missing > connect between both sentences.
No. Zen2/Rome has MSR_SPEC_CTRL. The point is that Zen2 and later shouldn't be using MSR_AMD64_LS_CFG in the first place. I'll tweak the wording. > >> Implement the algorithm given in AMD's SSBD whitepaper, and leave a >> printk_once() behind in the case that no controls can be found. >> >> This now means that a user explicitly choosing `spec-ctrl=ssbd` will properly >> turn off Memory Disambiguation on Fam19h/Zen3 systems. >> >> This still remains a single system-wide setting (for now), and is not context >> switched between vCPUs. As such, it doesn't interact with Intel's use of >> MSR_SPEC_CTRL and default_xen_spec_ctrl (yet). >> >> Signed-off-by: Andrew Cooper <[email protected]> > Reviewed-by: Jan Beulich <[email protected]> Thanks. ~Andrew
