Messages in this thread | | | Subject | Re: [PATCH v3 3/4] iommu: Add iommu_aux_get_domain_for_dev() | From | Lu Baolu <> | Date | Fri, 31 Jul 2020 14:30:03 +0800 |
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Hi Alex,
On 2020/7/30 4:25, Alex Williamson wrote: > On Tue, 14 Jul 2020 13:57:02 +0800 > Lu Baolu<baolu.lu@linux.intel.com> 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@redhat.com> >> Signed-off-by: Lu Baolu<baolu.lu@linux.intel.com> >> --- >> 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@x1.home/
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
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