Maybe no contract ... but a bunch of places (many of them in Intel
specific code) that check for it
arch/x86/events/core.c: if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
arch/x86/events/intel/core.c: if (!boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/events/intel/core.c: int assume = 3 * !boot_cpu_has(X86_FEATURE_HYPERVISOR);
arch/x86/events/intel/cstate.c: if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/events/intel/uncore.c: if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/kernel/apic/apic.c: if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/kernel/cpu/bugs.c: if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/kernel/cpu/bugs.c: else if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/kernel/cpu/bugs.c: if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
arch/x86/kernel/cpu/bugs.c: if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
arch/x86/kernel/cpu/intel.c: if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/kernel/cpu/mshyperv.c: if (!boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/kernel/cpu/vmware.c: * If !boot_cpu_has(X86_FEATURE_HYPERVISOR), vmware_hypercall_mode
arch/x86/kernel/cpu/vmware.c: if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
arch/x86/kernel/jailhouse.c: !boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/kernel/kvm.c: if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/kernel/paravirt.c: if (!boot_cpu_has(X86_FEATURE_HYPERVISOR))
arch/x86/kernel/tsc.c: if (boot_cpu_has(X86_FEATURE_HYPERVISOR) ||
arch/x86/mm/init_64.c: if (!boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
drivers/acpi/processor_idle.c: if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
drivers/gpu/drm/amd/amdgpu/amdgpu_virt.h: return boot_cpu_has(X86_FEATURE_HYPERVISOR);
drivers/gpu/drm/i915/i915_memcpy.c: !boot_cpu_has(X86_FEATURE_HYPERVISOR))
drivers/gpu/drm/radeon/radeon_device.c: return boot_cpu_has(X86_FEATURE_HYPERVISOR);
drivers/visorbus/visorchipset.c: if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {