By: Doug S (foo.delete@this.bar.bar), October 14, 2021 10:23 pm
Room: Moderated Discussions
rwessel (rwessel.delete@this.yahoo.com) on October 14, 2021 7:07 pm wrote:
> While dealing with that on-die can be dealt with by just not putting two incompatible cores on a
> die, that leaves the intra-cluster and VM migration issues with obvious solution. You could demand
> that the cluster (or potential VM migration targets) all have the same specs in this regard, but
> that seems a bit painful. The instruction definitions appear to define exceptions for when things
> like that happen, and so fixing it up in software ought to be possible. Still a bit ugly.
I'm tempted to say that if you choose to have incompatible ARM hardware in a VM cluster you deserve what you get...
At any rate that's something for the hypervisor to address - it should have a way to enforce or at least define the "lowest common denominator" for this any other hardware differences that might arise. This is potentially a much larger problem as you can have differences in cache line size, page size, ARMvX.Y version etc.
This isn't limited to ARM. You might run into potential issues if you mixed Intel and AMD hardware in a single VM cluster. I'd say you get what you deserve if you try it and experience issues.
> While dealing with that on-die can be dealt with by just not putting two incompatible cores on a
> die, that leaves the intra-cluster and VM migration issues with obvious solution. You could demand
> that the cluster (or potential VM migration targets) all have the same specs in this regard, but
> that seems a bit painful. The instruction definitions appear to define exceptions for when things
> like that happen, and so fixing it up in software ought to be possible. Still a bit ugly.
I'm tempted to say that if you choose to have incompatible ARM hardware in a VM cluster you deserve what you get...
At any rate that's something for the hypervisor to address - it should have a way to enforce or at least define the "lowest common denominator" for this any other hardware differences that might arise. This is potentially a much larger problem as you can have differences in cache line size, page size, ARMvX.Y version etc.
This isn't limited to ARM. You might run into potential issues if you mixed Intel and AMD hardware in a single VM cluster. I'd say you get what you deserve if you try it and experience issues.