9b4cf107b0
Certain configurations do not allow SynIC to be used in QEMU. In particular, - when hyperv_vpindex is off, SINT routes can't be used as they refer to the destination vCPU by vp_index - older KVM (which doesn't expose KVM_CAP_HYPERV_SYNIC2) zeroes out SynIC message and event pages on every msr load, breaking migration OTOH in-KVM users of SynIC -- SynIC timers -- do work in those configurations, and we shouldn't stop the guest from using them. To cover both scenarios, introduce an X86CPU property that makes CPU init code to skip creation of the SynIC object (and thus disables any SynIC use in QEMU) but keeps the KVM part of the SynIC working. The property is clear by default but is set via compat logic for older machine types. As a result, when hv_synic and a modern machine type are specified, QEMU will refuse to run unless vp_index is on and the kernel is recent enough. OTOH with an older machine type QEMU will run fine with hv_synic=on against an older kernel and/or without vp_index enabled but will disallow the in-QEMU uses of SynIC (in e.g. VMBus). Signed-off-by: Roman Kagan <rkagan@virtuozzo.com> Message-Id: <20180921082217.29481-4-rkagan@virtuozzo.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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