Avi Kivity <a...@redhat.com> wrote:
> > I have one concern about correctness issue though:
> >
> > concurrent rmap write protection may not be safe due to
> > delayed tlb flush ... cannot happen?
>
> What do you mean by concurrent rmap write protection?
>
Not sure, but other codes like:
- mmu_sync_children()
for_each_sp(pages, sp, parents, i)
protected |= rmap_write_protect(vcpu->kvm, sp->gfn);
if (protected)
kvm_flush_remote_tlbs(vcpu->kvm);
- kvm_mmu_get_page()
if (rmap_write_protect(vcpu->kvm, gfn))
kvm_flush_remote_tlbs(vcpu->kvm);
I just wondered what can happen if GET_DIRTY_LOG is being processed
behind these processing?
They may find nothing to write protect and won't do kvm_flush_remote_tlbs()
if the gfn has been already protected by GET_DIRTY_LOG.
But GET_DIRTY_LOG may still be busy write protecting other pages and
others can return before. (My code releases mmu_lock to not include
__put_user() in the critical section.)
I am not still enough familier with these code yet.
(maybe empty concern)
Takuya
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