KVM: lock slots_lock around device assignment (21a1416a) · Commits · 戴 / test

As pointed out by Jason Baron, when assigning a device to a guest we first set the iommu domain pointer, which enables mapping and unmapping of memory slots to the iommu. This leaves a window where this path is enabled, but we haven't synchronized the iommu mappings to the existing memory slots. Thus a slot being removed at that point could send us down unexpected code paths removing non-existent pinnings and iommu mappings. Take the slots_lock around creating the iommu domain and initial mappings as well as around iommu teardown to avoid this race. Signed-off-by:

Alex Williamson <alex.williamson@redhat.com> Signed-off-by:

Marcelo Tosatti <mtosatti@redhat.com>

virt/kvm/iommu.c

+15 −8

Original line number	Diff line number	Diff line
		@@ -240,9 +240,13 @@ int kvm_iommu_map_guest(struct kvm *kvm)
		return -ENODEV;
		}

		mutex_lock(&kvm->slots_lock);

		kvm->arch.iommu_domain = iommu_domain_alloc(&pci_bus_type);
		if (!kvm->arch.iommu_domain)
		return -ENOMEM;
		if (!kvm->arch.iommu_domain) {
		r = -ENOMEM;
		goto out_unlock;
		}

		if (!allow_unsafe_assigned_interrupts &&
		!iommu_domain_has_cap(kvm->arch.iommu_domain,
		@@ -253,17 +257,16 @@ int kvm_iommu_map_guest(struct kvm *kvm)
		" module option.\n", __func__);
		iommu_domain_free(kvm->arch.iommu_domain);
		kvm->arch.iommu_domain = NULL;
		return -EPERM;
		r = -EPERM;
		goto out_unlock;
		}

		r = kvm_iommu_map_memslots(kvm);
		if (r)
		goto out_unmap;

		return 0;

		out_unmap:
		kvm_iommu_unmap_memslots(kvm);

		out_unlock:
		mutex_unlock(&kvm->slots_lock);
		return r;
		}

		@@ -340,7 +343,11 @@ int kvm_iommu_unmap_guest(struct kvm *kvm)
		if (!domain)
		return 0;

		mutex_lock(&kvm->slots_lock);
		kvm_iommu_unmap_memslots(kvm);
		kvm->arch.iommu_domain = NULL;
		mutex_unlock(&kvm->slots_lock);

		iommu_domain_free(domain);
		return 0;
		}

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