[PATCH] kvm: lock slots_lock around device assignment

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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@xxxxxxxxxx>

 virt/kvm/iommu.c |   23 +++++++++++++++--------
 1 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/virt/kvm/iommu.c b/virt/kvm/iommu.c
index fec1723..e9fff98 100644
--- a/virt/kvm/iommu.c
+++ b/virt/kvm/iommu.c
@@ -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 &&
@@ -253,17 +257,16 @@ int kvm_iommu_map_guest(struct kvm *kvm)
 		       " module option.\n", __func__);
 		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;
+		kvm_iommu_unmap_memslots(kvm);
-	kvm_iommu_unmap_memslots(kvm);
+	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->arch.iommu_domain = NULL;
+	mutex_unlock(&kvm->slots_lock);
 	return 0;

To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html

[KVM ARM]     [KVM ia64]     [KVM ppc]     [Spice Development]     [Libvirt]     [Libvirt Users]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Photo]     [Yosemite News]    [Yosemite Photos]    [Linux Kernel]     [Linux SCSI]     [XFree86]

Add to Google Powered by Linux