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. > 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]> Jan
