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Oliver Upton
66570e966d
KVM unconditionally provides PV features to the guest, regardless of the configured CPUID. An unwitting guest that doesn't check KVM_CPUID_FEATURES before use could access paravirt features that userspace did not intend to provide. Fix this by checking the guest's CPUID before performing any paravirtual operations. Introduce a capability, KVM_CAP_ENFORCE_PV_FEATURE_CPUID, to gate the aforementioned enforcement. Migrating a VM from a host w/o this patch to a host with this patch could silently change the ABI exposed to the guest, warranting that we default to the old behavior and opt-in for the new one. Reviewed-by: Jim Mattson <[email protected]> Reviewed-by: Peter Shier <[email protected]> Signed-off-by: Oliver Upton <[email protected]> Change-Id: I202a0926f65035b872bfe8ad15307c026de59a98 Message-Id: <[email protected]> Reviewed-by: Wanpeng Li <[email protected]> Signed-off-by: Paolo Bonzini <[email protected]>