[PATCH v3 0/5] KVM: MMU: unify and cleanup the code of walking pte list

[Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>]

Current code has two ways to walk pte_list, the one is pte_list_walk and
the another way is rmap_get_first and rmap_get_next, they have the same logic.
This patchset tries to unify the code and also make the code more tidy.

Patch 1: KVM: MMU: introduce mmu_spte_establish, which tries to eliminates
the different between walking parent pte list and rmap, prepare for the
later patch.

Patch 2: KVM: MMU: clarify the logic in kvm_set_pte_rmapp, which prepares for
the next patch, no logic changed.

Patch 3: KVM: MMU: unify the code of walking pte list, unify the walking code.

Patch 4: KVM: MMU: fix spte assertion, fix a minor bug and remove the duplicate
code.

Patch 5: KVM: MMU: fast drop all spte on the pte_list, optimize for dropping
all sptes on rmap and remove all the "goto restart" pattern introduced by
the Patch 3.

Marcelo, Gleb, please apply them after applying the patchset of
[PATCH v3 0/3] KVM: MMU: simple cleanups.

Changelog:
v3:
- address Gleb's comments, remove the remained "goto restart" in
  kvm_set_pte_rmapp
- improve the changelog

Thanks!