Messages in this thread | | | Date | Thu, 2 Feb 2012 23:44:50 +0900 | From | Takuya Yoshikawa <> | Subject | Re: [test result] dirty logging without srcu update -- Re: [RFC][PATCH] srcu: Implement call_srcu() |
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Avi Kivity <avi@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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