Re: [PATCH v5 12/19] KVM: Move memslot deletion to helper function

Peter Xu
2020-02-06T16:14:24Z

On Tue, Jan 21, 2020 at 02:31:50PM -0800, Sean Christopherson wrote:
> Move memslot deletion into its own routine so that the success path for
> other memslot updates does not need to use kvm_free_memslot(), i.e. can
> explicitly destroy the dirty bitmap when necessary. This paves the way
> for dropping @dont from kvm_free_memslot(), i.e. all callers now pass
> NULL for @dont.
>
> Add a comment above the code to make a copy of the existing memslot
> prior to deletion, it is not at all obvious that the pointer will become
> stale during sorting and/or installation of new memslots.

Could you help explain a bit on this explicit comment? I can follow
up with the patch itself which looks all correct to me, but I failed
to catch what this extra comment wants to emphasize...

Thanks,

>
> Note, kvm_arch_commit_memory_region() allows an architecture to free
> resources when moving a memslot or changing its flags, e.g. x86 frees
> its arch specific memslot metadata during commit_memory_region().

--
Peter Xu