iommu: Fix deferred domain attachment

The IOMMU core code has support for deferring the attachment of a domain
to a device. This is needed in kdump kernels where the new domain must
not be attached to a device before the device driver takes it over.

When the AMD IOMMU driver got converted to use the dma-iommu
implementation, the deferred attaching got lost. The code in
dma-iommu.c has support for deferred attaching, but it calls into
iommu_attach_device() to actually do it. But iommu_attach_device()
will check if the device should be deferred in it code-path and do
nothing, breaking deferred attachment.

Move the is_deferred_attach() check out of the attach_device path and
into iommu_group_add_device() to make deferred attaching work from the
dma-iommu code.

Fixes: c53afe618ca9 ("iommu/dma-iommu: Handle deferred devices")
Reported-by: Jerry Snitselaar <jsnitsel@redhat.com>
Suggested-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Tested-by: Jerry Snitselaar <jsnitsel@redhat.com>
Cc: Jerry Snitselaar <jsnitsel@redhat.com>
Cc: Tom Murphy <murphyt7@tcd.ie>
Cc: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/20200519130340.14564-1-joro@8bytes.org

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 7b375421afba9ad4d91d424ed1eb2d7e51827f4d..1faa08c8bbb4dd3f39853fc357d49c4ac9c7364c 100644 (file)
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -693,6 +693,15 @@ out:
        return ret;
 }
 
+static bool iommu_is_attach_deferred(struct iommu_domain *domain,
+                                    struct device *dev)
+{
+       if (domain->ops->is_attach_deferred)
+               return domain->ops->is_attach_deferred(domain, dev);
+
+       return false;
+}
+
 /**
  * iommu_group_add_device - add a device to an iommu group
  * @group: the group into which to add the device (reference should be held)
@@ -747,7 +756,7 @@ rename:
 
        mutex_lock(&group->mutex);
        list_add_tail(&device->list, &group->devices);
-       if (group->domain)
+       if (group->domain  && !iommu_is_attach_deferred(group->domain, dev))
                ret = __iommu_attach_device(group->domain, dev);
        mutex_unlock(&group->mutex);
        if (ret)
@@ -1653,9 +1662,6 @@ static int __iommu_attach_device(struct iommu_domain *domain,
                                 struct device *dev)
 {
        int ret;
-       if ((domain->ops->is_attach_deferred != NULL) &&
-           domain->ops->is_attach_deferred(domain, dev))
-               return 0;
 
        if (unlikely(domain->ops->attach_dev == NULL))
                return -ENODEV;
@@ -1727,8 +1733,7 @@ EXPORT_SYMBOL_GPL(iommu_sva_unbind_gpasid);
 static void __iommu_detach_device(struct iommu_domain *domain,
                                  struct device *dev)
 {
-       if ((domain->ops->is_attach_deferred != NULL) &&
-           domain->ops->is_attach_deferred(domain, dev))
+       if (iommu_is_attach_deferred(domain, dev))
                return;
 
        if (unlikely(domain->ops->detach_dev == NULL))