Re: [PATCH 5/6] KVM: x86/mmu: Protect kvm->memslots with a mutex
From: Paolo Bonzini
Date: Wed Apr 28 2021 - 02:25:51 EST
On 28/04/21 00:36, Ben Gardon wrote:
+void kvm_arch_assign_memslots(struct kvm *kvm, int as_id,
+ struct kvm_memslots *slots)
+{
+ mutex_lock(&kvm->arch.memslot_assignment_lock);
+ rcu_assign_pointer(kvm->memslots[as_id], slots);
+ mutex_unlock(&kvm->arch.memslot_assignment_lock);
+}
Does the assignment also needs the lock, or only the rmap allocation? I
would prefer the hook to be something like kvm_arch_setup_new_memslots.
(Also it is useful to have a comment somewhere explaining why the
slots_lock does not work. IIUC there would be a deadlock because you'd
be taking the slots_lock inside an SRCU critical region, while usually
the slots_lock critical section is the one that includes a
synchronize_srcu; I should dig that up and document that ordering in
Documentation/virt/kvm too).
Paolo