On Thu, 18 Dec 2014, Paolo Bonzini wrote: > On 18/12/2014 04:37, zhanghailiang wrote: > >> set this bit. But the HV_X64_APIC_ACCESS_RECOMMENDED bit should > >> probably not be set if the host supports apic-v. I havn't done any > > > > That is what this patch want to do ;) > > This would cause a guest ABI change upon migration from APICv to > non-APICv hosts, so it is not possible. Perhaps we need to set bit 8 > but not bit 3. I think setting the "recommended" bits to be best for the host where the VM is first started should always be ok. When it migrates to a different host, performance may not be optimal but otherwise it will work just fine. After all, non-optimal performance is not different from the current situation. It's important not to change the "supported" bits dynamically, though. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
