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Stéphane Lesimple
b8b2f8377b
Inside a Xen PVH domU (and any guest where the kernel sets
X86_FEATURE_HYPERVISOR), the kernel appends "; SMT Host state unknown"
to the MDS/MMIO sysfs vuln string: the host controls SMT scheduling and
the guest genuinely can't see it. The "SMT is either mitigated or
disabled" check only matched 'SMT (disabled|mitigated)', so this read as
"not mitigated" and --paranoid flipped the verdict to a misleading
VULN "you must disable SMT (Hyper-Threading)".
Make *_smt_mitigated a tri-state: 1 (disabled/mitigated), 0 (vulnerable),
and 2 (host state unknown). In paranoid mode, when the in-guest
mitigation is active but SMT host state is unknown, report UNK with an
explanation that cross-thread protection depends on the hypervisor host's
SMT/core-scheduling config, instead of VULN. PV DomUs (kernel reports
"SMT vulnerable", no HYPERVISOR bit) are unchanged and still flagged.
(cherry picked from commit 1e33f40f0a)