1 Oct
2021
1 Oct
'21
2:07 p.m.
On 01/10/2021 14:33, Jane Malalane wrote:
Currently, Linux probes for X86_BUG_NULL_SEL unconditionally which makes it unsafe to migrate in a virtualised environment as the properties across the migration pool might differ.
Zen3 adds the NullSelectorClearsBase bit to indicate that loading a NULL segment selector zeroes the base and limit fields, as well as just attributes. Zen2 also has this behaviour but doesn't have the NSCB bit.
When virtualised, NSCB might be cleared for migration safety, therefore we must not probe. Always honour the NSCB bit in this case, as the hypervisor is expected to synthesize it in the Zen2 case.
Signed-off-by: Jane Malalane jane.malalane@citrix.com
Reviewed-by: Andrew Cooper andrew.cooper3@citrix.com