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@xxxxxxxxxx>
Cc: Gleb Natapov <gleb@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
virt/kvm/vfio.c | 27 ++++++++++++++++++++-------
1 file changed, 20 insertions(+), 7 deletions(-)
diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
index b4f9507..ba1a93f 100644
--- a/virt/kvm/vfio.c
+++ b/virt/kvm/vfio.c
@@ -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) {
--
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