* Tobin Feldman-Fitzthum (tobin@xxxxxxxxxxxxx) wrote: > On 8/18/21 3:04 PM, Dr. David Alan Gilbert wrote: > > * Tobin Feldman-Fitzthum (tobin@xxxxxxxxxxxxx) wrote: > > > On 8/17/21 6:04 PM, Steve Rutherford wrote: > > > > Ahh, It sounds like you are looking into sidestepping the existing > > > > AMD-SP flows for migration. I assume the idea is to spin up a VM on > > > > the target side, and have the two VMs attest to each other. How do the > > > > two sides know if the other is legitimate? I take it that the source > > > > is directing the LAUNCH flows? > > > Yeah we don't use PSP migration flows at all. We don't need to send the MH > > > code from the source to the target because the MH lives in firmware, which > > > is common between the two. > > Are you relying on the target firmware to be *identical* or purely for > > it to be *compatible* ? It's normal for a migration to be the result of > > wanting to do an upgrade; and that means the destination build of OVMF > > might be newer (or older, or ...). > > > > Dave > > This is a good point. The migration handler on the source and target must > have the same memory footprint or bad things will happen. Using the same > firmware on the source and target is an easy way to guarantee this. Since > the MH in OVMF is not a contiguous region of memory, but a group of > functions scattered around OVMF, it is a bit difficult to guarantee that the > memory footprint is the same if the build is different. Can you explain what the 'memory footprint' consists of? Can't it just be the whole of the OVMF rom space if you have no way of nudging the MH into it's own chunk? I think it really does have to cope with migration to a new version of host. Dave > -Tobin > > > > > > > > We start the target like a normal VM rather than > > > waiting for an incoming migration. The plan is to treat the target like a > > > normal VM for attestation as well. The guest owner will attest the target VM > > > just like they would any other VM that is started on their behalf. Secret > > > injection can be used to establish a shared key for the source and target. > > > > > > -Tobin > > > > > > > --Steve > > > > > -- Dr. David Alan Gilbert / dgilbert@xxxxxxxxxx / Manchester, UK
