Re: [PATCH v13 11/35] KVM: Drop .on_unlock() mmu_notifier hook

[Paolo Bonzini]

On 10/27/23 20:21, Sean Christopherson wrote:
> Drop the .on_unlock() mmu_notifer hook now that it's no longer used for
> notifying arch code that memory has been reclaimed.  Adding .on_unlock()
> and invoking it *after* dropping mmu_lock was a terrible idea, as doing so
> resulted in .on_lock() and .on_unlock() having divergent and asymmetric
> behavior, and set future developers up for failure, i.e. all but asked for
> bugs where KVM relied on using .on_unlock() to try to run a callback while
> holding mmu_lock.
>
> Opportunistically add a lockdep assertion in kvm_mmu_invalidate_end() to
> guard against future bugs of this nature.

This is what David suggested to do in patch 3, FWIW.

Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>

Paolo

> Reported-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> Link: https://lore.kernel.org/all/20230802203119.GB2021422@xxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---