Messages in this thread | | | Date | Wed, 14 Mar 2012 14:34:32 +0900 | From | Takuya Yoshikawa <> | Subject | Re: [PATCH 2/4] KVM: Avoid checking huge page mappings in get_dirty_log() |
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Marcelo Tosatti <mtosatti@redhat.com> wrote:
> guest fault enable dirty logging > > tdp_page_fault (all _page_fault functions) kvm_set_memory_region > > > level = mapping_level(vcpu, gfn) > (finds level == 2 or 3) > > > rcu_assign_pointer(slot > with > ->dirty_bitmap) > synchronize_srcu_expedited()
Isn't here still in the SRCU read-side critical section?
> schedule() > kvm_arch_commit_memory_region() > spin_lock(mmu_lock) > kvm_mmu_slot_remove_write_access() > removes large sptes > spin_unlock(mmu_lock) > spin_lock(mmu_lock) > create large spte accordingly > to level above > spin_unlock(mmu_lock) >
If so, we cannot start kvm_arch_commit_memory_region() until the completion of the SRCU critical section and this race will not happen.
Takuya
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