On 12/22/21 2:46 AM, Jason Gunthorpe wrote:
It's worth taking a step back and realising that overall, this is really
just a more generalised and finer-grained extension of what 426a273834ea
already did for non-group-aware code, so it makes little sense*not* to
integrate it into the existing interfaces.
This is taking 426a to it's logical conclusion and*removing* the
group API from the drivers entirely. This is desirable because drivers
cannot do anything sane with the group.
The drivers have struct devices, and so we provide APIs that work in
terms of struct devices to cover both driver use cases today, and do
so more safely than what is already implemented.
Do not mix up VFIO with the driver interface, these are different
things. It is better VFIO stay on its own and not complicate the
driver world.
Per Joerg's previous comments:
https://lore.kernel.org/linux-iommu/20211119150612.jhsvsbzisvux2lga@xxxxxxxxxx/
The commit 426a273834ea came only in order to disallow attaching a
single device within a group to a different iommu_domain. So it's
reasonable to improve the existing iommu_attach/detach_device() to cover
all cases. How about below code? Did I miss anything?
int iommu_attach_device(struct iommu_domain *domain, struct device *dev)
{
struct iommu_group *group;
int ret = 0;
group = iommu_group_get(dev);
if (!group)
return -ENODEV;
mutex_lock(&group->mutex);
if (group->attach_cnt) {
if (group->domain != domain) {
ret = -EBUSY;
goto unlock_out;
}
} else {
ret = __iommu_attach_group(domain, group);
if (ret)
goto unlock_out;
}
group->attach_cnt++;
unlock_out:
mutex_unlock(&group->mutex);
iommu_group_put(group);
return ret;
}
EXPORT_SYMBOL_GPL(iommu_attach_device);
void iommu_detach_device_shared(struct iommu_domain *domain, struct
device *dev)
{
struct iommu_group *group;
group = iommu_group_get(dev);
if (WARN_ON(!group))
return;
mutex_lock(&group->mutex);
if (WARN_ON(!group->attach_cnt || group->domain != domain)
goto unlock_out;
if (--group->attach_cnt == 0)
__iommu_detach_group(domain, group);
unlock_out:
mutex_unlock(&group->mutex);
iommu_group_put(group);
}
EXPORT_SYMBOL_GPL(iommu_detach_device);
Best regards,
baolu
