KVM: x86: too many kworkers created during VM boot

Merge Request Required Information

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2210042

Summary of Changes

Backport fixes to fix excessive unloading of TDP MMU roots when CR0.WP changes or when going in/out of SMM.

Unlike the shadow MMU, the TDP MMU doesn't track "inactive" roots in a per-VM structure, where "active" in this case means a root is either in-use or cached as a previous root by at least one vCPU. When a TDP MMU root becomes inactive, i.e. the last vCPU reference to the root is put, for all intents and purposes the root is gone.

Approved Development Ticket

https://issues.redhat.com/browse/RHELPLAN-158211

Depends: https://bugzilla.redhat.com/show_bug.cgi?id=2177720

Depends: !2467 (merged)

Signed-off-by: Paolo Bonzini pbonzini@redhat.com