Re: [PATCH 09/10] KVM: x86: MMU: Move parent_pte handling from kvm_mmu_get_page() to link_shadow_page()

[Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>]

On 2015/11/26 1:32, Paolo Bonzini wrote:
> On 20/11/2015 09:57, Xiao Guangrong wrote:

>> You can move this patch to the front of
>> [PATCH 08/10] KVM: x86: MMU: Use for_each_rmap_spte macro instead of
>> pte_list_walk()
>>
>> By moving kvm_mmu_mark_parents_unsync() to the behind of mmu_spte_set()
>> (then the parent
>> spte is present now), you can directly clean up for_each_rmap_spte().
>
> So basically squash together the two patches (8/10 and 9/10) except the
> change to kvm_mmu_mark_parents_unsync; then in the second patch switch
> from pte_list_walk to for_each_rmap_spte.
>
> That makes sense indeed.

Sorry for my being late to respond to Xiao's suggestions.  I could not
use my development machine for a while this week.

In short, this kvm_mmu_mark_parents_unsync() call in kvm_mmu_get_page()
should have been mark_unsync() for the new parent_pte only, because we
are constructing the mappings from/to it and other parents in the
sp->parent_ptes are not related to this fault?

As the code has been this way for some time, a bit scary to change it,
but I'll do some tests without that extra kvm_mmu_mark_parents_unsync()
with a guest (with ept=0) this afternoon.

   Takuya