This series started from looking at mmu_unsync_walk for the ubsan thread.
Patches 1 and 2 are the result of the discussions in that thread.
Patches 3 to 9 do more cleanups in __kvm_sync_page and its callers.
Among other changes, it removes kvm_sync_page_transient and avoids
duplicate code between __kvm_sync_page and kvm_sync_pages.
I stopped where I had questions about the existing kvm_mmu_get_page
code (see patch 8 for the question). However perhaps more cleanups
are possible, also thanks to Takuya's work on that function and
link_shadow_page.
Patches 10 to 12 are just micro-optimizations.
Guangrong, it would be great if you took a look since you know this part
of KVM very well.