On Sun, Dec 11, 2022, Zhang Chen wrote: > From: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx> > > Guests that have different family/model than the host may not be aware > of hardware mitigations(such as RRSBA_DIS_S) available on host. This is > particularly true when guests migrate. To solve this problem Intel > processors have added a virtual MSR interface Is there any actual "processor" support here? To me, this looks like Intel is foisting a paravirt interface on KVM and other hypervisors without collaborating with said hypervisors' developers and maintainers. I get that some of the mitigations are vendor specific, but things like RETPOLINE aren't vendor specific. I haven't followed all of the mitigation stuff very closely, but I wouldn't be surprised if there are mitigations now or in the future that are common across architectures, e.g. arm64 and x86-64. Intel doing its own thing means AMD and arm64 will likely follow suit, and suddenly KVM is supporting multiple paravirt interfaces for very similar things, without having any control over the APIs. That's all kinds of backwards. And having to wait for Intel to roll out new documentation when software inevitably comes up with some clever new mitigation doesn't exactly fill my heart with joy.
