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Vixen: A PV-in-HVM shim
- aliguori 9y agoWe're still working the details out upstream but the TL;DR is that the way to address Meltdown with Xen PV is to use nested virtualization so that the outer guest is an HVM or PVH guest.
- jlgaddis 9y agoIs this what AWS is doing?
- aliguori 9y agoYes, all customer PV instances in EC2 are running in an HVM container and are protected against the guest-to-guest Meltdown vulnerability. As with all virtual and physical machines, patches are necessary to protect against process-to-process Meltdown within the OS itself. Those are starting to roll out from the respective vendors although it will take time for those to work inside a PV instance.
- Vogtinator 9y agoDoesn't this still allow to read memory from the hypervisor shared between the PV VMs in a HVM container?
- bonzini 9y agoNo, because page tables are isolated between guests.
- cthalupa 9y agoThe intention, from my understanding, is not to boot multiple PV guests inside of one HVM shim, but instead treat it as more of a packaged deal - for each PV guest, you will be running it inside an independent vixen shim. So 5 PV guests, 5 vixen shims, etc.
- quanstro 9y agocorrect.
- jacobn 9y agoFrom the post: "all PV instances in EC2 are using this"
- jlgaddis 9y agoYeah, thanks, not sure HTF I missed that the first time.
- darren0 9y agoPV in HVM, not to be confused with PV on HVM [1] which includes PVHVM and HVM + PV drivers :) [1] https://wiki.xen.org/wiki/PV_on_HVM https://wiki.xen.org/wiki/PV_on_HVM
- snvzz 9y agoIt sure gets complicated. https://wiki.xen.org/wiki/Virtualization_Spectrum#The_paravirtualization_spectrum https://wiki.xen.org/wiki/Virtualization_Spectrum#The_paravi...