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kvm/vfio: Support for DMA coherent IOMMUs

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VFIO now has support for using the IOMMU_CACHE flag and a mechanism
for an external user to test the current operating mode of the IOMMU.
Add support for this to the kvm-vfio pseudo device so that we only
register noncoherent DMA when necessary.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Alex Williamson 2014-02-26 11:38:40 -07:00
parent 88d7ab8949
commit 9d830d47c7
1 changed files with 20 additions and 7 deletions
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27
virt/kvm/vfio.c
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@ -59,6 +59,22 @@ static void kvm_vfio_group_put_external_user(struct vfio_group *vfio_group)
symbol_put(vfio_group_put_external_user);
}
static bool kvm_vfio_group_is_coherent(struct vfio_group *vfio_group)
{
long (*fn)(struct vfio_group *, unsigned long);
long ret;
fn = symbol_get(vfio_external_check_extension);
if (!fn)
return false;
ret = fn(vfio_group, VFIO_DMA_CC_IOMMU);
symbol_put(vfio_external_check_extension);
return ret > 0;
}
/*
* 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
@ -75,13 +91,10 @@ static void kvm_vfio_update_coherency(struct kvm_device *dev)
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 (!kvm_vfio_group_is_coherent(kvg->vfio_group)) {
noncoherent = true;
break;
}
}
if (noncoherent != kv->noncoherent) {