Re: [PATCH 00/14] KVM: x86/mmu: Dirty logging fixes and improvements

[Sean Christopherson]

On Fri, Feb 12, 2021, Sean Christopherson wrote:
> Paolo, this is more or less ready, but on final read-through before
> sending I realized it would be a good idea to WARN during VM destruction
> if cpu_dirty_logging_count is non-zero.  I wanted to get you this before
> the 5.12 window opens in case you want the TDP MMU fixes for 5.12.  I'll
> do the above change and retest next week (note, Monday is a US holiday).

Verified cpu_dirty_logging_count does indeed hit zero during VM destruction.

Adding a WARN to KVM would require adding an arch hook to kvm_free_memslots(),
otherwise the count will be non-zero if the VM is destroyed with dirty logging
active.  That doesn't seem worthwhile, so I'm not planning on pursuing a WARN
for the upstream code.