Hi Alex,
On 2020/7/30 4:25, Alex Williamson wrote:
On Tue, 14 Jul 2020 13:57:02 +0800
Lu Baolu<baolu.lu@xxxxxxxxxxxxxxx> wrote:
The device driver needs an API to get its aux-domain. A typical usage
scenario is:
unsigned long pasid;
struct iommu_domain *domain;
struct device *dev = mdev_dev(mdev);
struct device *iommu_device = vfio_mdev_get_iommu_device(dev);
domain = iommu_aux_get_domain_for_dev(dev);
if (!domain)
return -ENODEV;
pasid = iommu_aux_get_pasid(domain, iommu_device);
if (pasid <= 0)
return -EINVAL;
/* Program the device context */
....
This adds an API for such use case.
Suggested-by: Alex Williamson<alex.williamson@xxxxxxxxxx>
Signed-off-by: Lu Baolu<baolu.lu@xxxxxxxxxxxxxxx>
---
drivers/iommu/iommu.c | 18 ++++++++++++++++++
include/linux/iommu.h | 7 +++++++
2 files changed, 25 insertions(+)
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index cad5a19ebf22..434bf42b6b9b 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2817,6 +2817,24 @@ void iommu_aux_detach_group(struct iommu_domain *domain,
}
EXPORT_SYMBOL_GPL(iommu_aux_detach_group);
+struct iommu_domain *iommu_aux_get_domain_for_dev(struct device *dev)
+{
+ struct iommu_domain *domain = NULL;
+ struct iommu_group *group;
+
+ group = iommu_group_get(dev);
+ if (!group)
+ return NULL;
+
+ if (group->aux_domain_attached)
+ domain = group->domain;
Why wouldn't the aux domain flag be on the domain itself rather than
the group? Then if we wanted sanity checking in patch 1/ we'd only
need to test the flag on the object we're provided.
Agreed. Given that a group may contain both non-aux and aux devices,
adding such flag in iommu_group doesn't make sense.
If we had such a flag, we could create an iommu_domain_is_aux()
function and then simply use iommu_get_domain_for_dev() and test that
it's an aux domain in the example use case. It seems like that would
resolve the jump from a domain to an aux-domain just as well as adding
this separate iommu_aux_get_domain_for_dev() interface. The is_aux
test might also be useful in other cases too.
Let's rehearsal our use case.
unsigned long pasid;
struct iommu_domain *domain;
struct device *dev = mdev_dev(mdev);
struct device *iommu_device = vfio_mdev_get_iommu_device(dev);
[1] domain = iommu_get_domain_for_dev(dev);
if (!domain)
return -ENODEV;
[2] pasid = iommu_aux_get_pasid(domain, iommu_device);
if (pasid <= 0)
return -EINVAL;
/* Program the device context */
....
The reason why I add this iommu_aux_get_domain_for_dev() is that we need
to make sure the domain got at [1] is valid to be used at [2].
https://lore.kernel.org/linux-iommu/20200707150408.474d81f1@xxxxxxx/
When calling into iommu_aux_get_pasid(), the iommu driver should make
sure that @domain is a valid aux-domain for @iommu_device. Hence, for
our use case, it seems that there's no need for a is_aux_domain() api.
Anyway, I'm not against adding a new is_aux_domain() api if there's a
need elsewhere.
Best regards,
baolu
