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Diffstat (limited to 'Documentation/virt/kvm/locking.rst')
| -rw-r--r-- | Documentation/virt/kvm/locking.rst | 22 |
1 files changed, 16 insertions, 6 deletions
diff --git a/Documentation/virt/kvm/locking.rst b/Documentation/virt/kvm/locking.rst index 845a561629f1..a0146793d197 100644 --- a/Documentation/virt/kvm/locking.rst +++ b/Documentation/virt/kvm/locking.rst @@ -16,20 +16,30 @@ The acquisition orders for mutexes are as follows: - kvm->slots_lock is taken outside kvm->irq_lock, though acquiring them together is quite rare. -- Unlike kvm->slots_lock, kvm->slots_arch_lock is released before - synchronize_srcu(&kvm->srcu). Therefore kvm->slots_arch_lock - can be taken inside a kvm->srcu read-side critical section, - while kvm->slots_lock cannot. - - kvm->mn_active_invalidate_count ensures that pairs of invalidate_range_start() and invalidate_range_end() callbacks use the same memslots array. kvm->slots_lock and kvm->slots_arch_lock are taken on the waiting side in install_new_memslots, so MMU notifiers must not take either kvm->slots_lock or kvm->slots_arch_lock. +For SRCU: + +- ``synchronize_srcu(&kvm->srcu)`` is called inside critical sections + for kvm->lock, vcpu->mutex and kvm->slots_lock. These locks _cannot_ + be taken inside a kvm->srcu read-side critical section; that is, the + following is broken:: + + srcu_read_lock(&kvm->srcu); + mutex_lock(&kvm->slots_lock); + +- kvm->slots_arch_lock instead is released before the call to + ``synchronize_srcu()``. It _can_ therefore be taken inside a + kvm->srcu read-side critical section, for example while processing + a vmexit. + On x86: -- vcpu->mutex is taken outside kvm->arch.hyperv.hv_lock +- vcpu->mutex is taken outside kvm->arch.hyperv.hv_lock and kvm->arch.xen.xen_lock - kvm->arch.mmu_lock is an rwlock. kvm->arch.tdp_mmu_pages_lock and kvm->arch.mmu_unsync_pages_lock are taken inside kvm->arch.mmu_lock, and |