On Tue, Dec 08, 2020 at 06:21:12PM +0000, Marc Zyngier wrote: > On 2020-12-08 17:21, Catalin Marinas wrote: > > On Mon, Dec 07, 2020 at 07:03:13PM +0000, Marc Zyngier wrote: > > > I wonder whether we will have to have something kernel side to > > > dump/reload tags in a way that matches the patterns used by live > > > migration. > > > > We have something related - ptrace dumps/resores the tags. Can the same > > concept be expanded to a KVM ioctl? > > Yes, although I wonder whether we should integrate this deeply into > the dirty-log mechanism: it would be really interesting to dump the > tags at the point where the page is flagged as clean from a dirty-log > point of view. As the page is dirtied, discard the saved tags. >From the VMM perspective, the tags can be treated just like additional (meta)data in a page. We'd only need the tags when copying over. It can race with the VM dirtying the page (writing tags would dirty it) but I don't think the current migration code cares about this. If dirtied, it copies it again. The only downside I see is an extra syscall per page both on the origin VMM and the destination one to dump/restore the tags. Is this a performance issue? -- Catalin _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
