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kvm: Create non-coherent DMA registeration

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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 <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
This commit is contained in:
Alex Williamson 2013-10-30 11:02:30 -06:00 • committed by Paolo Bonzini
commit e0f0bbc527
6 changed files with 92 additions and 4 deletions
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6
virt/kvm/iommu.c
View file

@ -140,6 +140,9 @@ static int kvm_iommu_map_memslots(struct kvm *kvm)
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 @@ static int kvm_iommu_unmap_memslots(struct kvm *kvm)
srcu_read_unlock(&kvm->srcu, idx);
if (kvm->arch.iommu_noncoherent)
kvm_arch_unregister_noncoherent_dma(kvm);
return 0;
}

44
virt/kvm/vfio.c
View file

@ -27,6 +27,7 @@ struct kvm_vfio_group {
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 @@ static void kvm_vfio_group_put_external_user(struct vfio_group *vfio_group)
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 @@ static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
mutex_unlock(&kv->lock);
kvm_vfio_update_coherency(dev);
return 0;
case KVM_DEV_VFIO_GROUP_DEL:
@ -140,6 +180,8 @@ static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
kvm_vfio_group_put_external_user(vfio_group);
kvm_vfio_update_coherency(dev);
return ret;
}
@ -185,6 +227,8 @@ static void kvm_vfio_destroy(struct kvm_device *dev)
kfree(kvg);
}
kvm_vfio_update_coherency(dev);
kfree(kv);
kfree(dev); /* alloc by kvm_ioctl_create_device, free by .destroy */
}