kvm: Create non-coherent DMA registeration
We currently use some ad-hoc arch variables tied to legacy KVM device
assignment to manage emulation of instructions that depend on whether
non-coherent DMA is present. Create an interface for this, adapting
legacy KVM device assignment and adding VFIO via the KVM-VFIO device.
For now we assume that non-coherent DMA is possible any time we have a
VFIO group. Eventually an interface can be developed as part of the
VFIO external user interface to query the coherency of a group.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/virt/kvm/iommu.c b/virt/kvm/iommu.c
index d32d156..c7d9ce1 100644
--- a/virt/kvm/iommu.c
+++ b/virt/kvm/iommu.c
@@ -140,6 +140,9 @@
struct kvm_memslots *slots;
struct kvm_memory_slot *memslot;
+ if (kvm->arch.iommu_noncoherent)
+ kvm_arch_register_noncoherent_dma(kvm);
+
idx = srcu_read_lock(&kvm->srcu);
slots = kvm_memslots(kvm);
@@ -327,6 +330,9 @@
srcu_read_unlock(&kvm->srcu, idx);
+ if (kvm->arch.iommu_noncoherent)
+ kvm_arch_unregister_noncoherent_dma(kvm);
+
return 0;
}
diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
index 597c258..ca4260e3 100644
--- a/virt/kvm/vfio.c
+++ b/virt/kvm/vfio.c
@@ -27,6 +27,7 @@
struct kvm_vfio {
struct list_head group_list;
struct mutex lock;
+ bool noncoherent;
};
static struct vfio_group *kvm_vfio_group_get_external_user(struct file *filep)
@@ -58,6 +59,43 @@
symbol_put(vfio_group_put_external_user);
}
+/*
+ * Groups can use the same or different IOMMU domains. If the same then
+ * adding a new group may change the coherency of groups we've previously
+ * been told about. We don't want to care about any of that so we retest
+ * each group and bail as soon as we find one that's noncoherent. This
+ * means we only ever [un]register_noncoherent_dma once for the whole device.
+ */
+static void kvm_vfio_update_coherency(struct kvm_device *dev)
+{
+ struct kvm_vfio *kv = dev->private;
+ bool noncoherent = false;
+ struct kvm_vfio_group *kvg;
+
+ mutex_lock(&kv->lock);
+
+ list_for_each_entry(kvg, &kv->group_list, node) {
+ /*
+ * TODO: We need an interface to check the coherency of
+ * the IOMMU domain this group is using. For now, assume
+ * it's always noncoherent.
+ */
+ noncoherent = true;
+ break;
+ }
+
+ if (noncoherent != kv->noncoherent) {
+ kv->noncoherent = noncoherent;
+
+ if (kv->noncoherent)
+ kvm_arch_register_noncoherent_dma(dev->kvm);
+ else
+ kvm_arch_unregister_noncoherent_dma(dev->kvm);
+ }
+
+ mutex_unlock(&kv->lock);
+}
+
static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
{
struct kvm_vfio *kv = dev->private;
@@ -105,6 +143,8 @@
mutex_unlock(&kv->lock);
+ kvm_vfio_update_coherency(dev);
+
return 0;
case KVM_DEV_VFIO_GROUP_DEL:
@@ -140,6 +180,8 @@
kvm_vfio_group_put_external_user(vfio_group);
+ kvm_vfio_update_coherency(dev);
+
return ret;
}
@@ -185,6 +227,8 @@
kfree(kvg);
}
+ kvm_vfio_update_coherency(dev);
+
kfree(kv);
kfree(dev); /* alloc by kvm_ioctl_create_device, free by .destroy */
}