[PATCH 5.6 021/126] iommu: Fix deferred domain attachment

From: Greg Kroah-Hartman
Date: Tue May 26 2020 - 15:21:41 EST

From: Joerg Roedel <jroedel@xxxxxxx>

[ Upstream commit bd421264ed307dd296eab036851221b225071a32 ]

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: 795bbbb9b6f8 ("iommu/dma-iommu: Handle deferred devices")
Reported-by: Jerry Snitselaar <jsnitsel@xxxxxxxxxx>
Suggested-by: Robin Murphy <robin.murphy@xxxxxxx>
Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
Tested-by: Jerry Snitselaar <jsnitsel@xxxxxxxxxx>
Cc: Jerry Snitselaar <jsnitsel@xxxxxxxxxx>
Cc: Tom Murphy <murphyt7@xxxxxx>
Cc: Robin Murphy <robin.murphy@xxxxxxx>
Link: https://lore.kernel.org/r/20200519130340.14564-1-joro@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/iommu/iommu.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 8d2477941fd9..22b28076d48e 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -692,6 +692,15 @@ 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)
@@ -746,7 +755,7 @@ rename:

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);
if (ret)
@@ -1652,9 +1661,6 @@ 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;
@@ -1726,8 +1732,7 @@ 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))

if (unlikely(domain->ops->detach_dev == NULL))