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Diffstat (limited to 'Documentation/virt/kvm/locking.rst')
| -rw-r--r-- | Documentation/virt/kvm/locking.rst | 25 |
1 files changed, 13 insertions, 12 deletions
diff --git a/Documentation/virt/kvm/locking.rst b/Documentation/virt/kvm/locking.rst index a3ca76f9be75..a0146793d197 100644 --- a/Documentation/virt/kvm/locking.rst +++ b/Documentation/virt/kvm/locking.rst @@ -24,21 +24,22 @@ The acquisition orders for mutexes are as follows: For SRCU: -- ``synchronize_srcu(&kvm->srcu)`` is called _inside_ - the kvm->slots_lock critical section, therefore kvm->slots_lock - cannot be taken inside a kvm->srcu read-side critical section. - Instead, kvm->slots_arch_lock is released before the call - to ``synchronize_srcu()`` and _can_ be taken inside a - kvm->srcu read-side critical section. - -- kvm->lock is taken inside kvm->srcu, therefore - ``synchronize_srcu(&kvm->srcu)`` cannot be called inside - a kvm->lock critical section. If you cannot delay the - call until after kvm->lock is released, use ``call_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 |