On Wed, Feb 12, 2020 at 09:42:02PM -0800, Andy Lutomirski wrote: >> On Wed, Feb 12, 2020 at 5:18 PM Ashish Kalra <Ashish.Kalra@xxxxxxx> wrote: >> > >> > From: Brijesh Singh <brijesh.singh@xxxxxxx> > > > > Invoke a hypercall when a memory region is changed from encrypted -> > > decrypted and vice versa. Hypervisor need to know the page encryption > > status during the guest migration. >> >> What happens if the guest memory status doesn't match what the >> hypervisor thinks it is? What happens if the guest gets migrated >> between the hypercall and the associated flushes? This is basically same as the dirty page tracking and logging being done during Live Migration. As with dirty page tracking and logging we maintain a page encryption bitmap in the kernel which keeps tracks of guest's page encrypted/decrypted state changes and this bitmap is sync'ed regularly from kernel to qemu and also during the live migration process, therefore any dirty pages whose encryption status will change during migration, should also have their page status updated when the page encryption bitmap is sync'ed. Also i think that when the amount of dirty pages reach a low threshold, QEMU stops the source VM and then transfers all the remaining dirty pages, so at that point, there will also be a final sync of the page encryption bitmap, there won't be any hypercalls after this as the source VM has been stopped and the remaining VM state gets transferred. Thanks, Ashish
