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Commit 9d830d47 authored by Alex Williamson's avatar Alex Williamson
Browse files

kvm/vfio: Support for DMA coherent IOMMUs 



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: default avatarAlex Williamson <alex.williamson@redhat.com>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 88d7ab89

virt/kvm/vfio.c

+20 −7
Original line number Diff line number Diff line
@@ -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
@@ -75,14 +91,11 @@ 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.

		 */

		if (!kvm_vfio_group_is_coherent(kvg->vfio_group)) {

			noncoherent = true;

			break;

		}

	}



	if (noncoherent != kv->noncoherent) {

		kv->noncoherent = noncoherent;