Anything is possible, but I would think that if it was fixable at that level we wouldn't have OS developers going through all of this trouble. There is basically no upside to this patch-set at all for the end-user except for increased security, and there's pretty big down-sides in the form of fairly significant speed losses.
Keep in mind, this is more-or-less just the 4GB/4GB patch set that floated around awhile back for 32-bit systems, and that patch was never merged precisely because of the big performance impact it imposed - and that change actually had some merit, this one has none besides security. I don't think Linus would be letting this go through (And especially be on by default) without a fuss unless there is really no other way to mitigate a fairly big security hole. That's just my opinion, but it seems pretty clear to me. It's possible he has not spoken to anybody at Intel about this, but I would personally think he has some connections to get some info on it.
Keep in mind, this is more-or-less just the 4GB/4GB patch set that floated around awhile back for 32-bit systems, and that patch was never merged precisely because of the big performance impact it imposed - and that change actually had some merit, this one has none besides security. I don't think Linus would be letting this go through (And especially be on by default) without a fuss unless there is really no other way to mitigate a fairly big security hole. That's just my opinion, but it seems pretty clear to me. It's possible he has not spoken to anybody at Intel about this, but I would personally think he has some connections to get some info on it.