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Andrew Cooper
e06b95c1d4
Currently, VERW flushing to mitigate MDS is boot time conditional per domain type. However, to provide mitigations for DRPW (CVE-2022-21166), we need to conditionally use VERW based on the trustworthiness of the guest, and the devices passed through. Remove the PV/HVM alternatives and instead issue a VERW on the return-to-guest path depending on the SCF_verw bit in cpuinfo spec_ctrl_flags. Introduce spec_ctrl_init_domain() and d->arch.verw to calculate the VERW disposition at domain creation time, and context switch the SCF_verw bit. For now, VERW flushing is used and controlled exactly as before, but later patches will add per-domain cases too. No change in behaviour. This is part of XSA-404. Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
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