Messages in this thread | | | Date | Mon, 15 Nov 2021 05:27:15 -0800 | From | Christoph Hellwig <> | Subject | Re: [PATCH 06/11] iommu: Expose group variants of dma ownership interfaces |
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On Mon, Nov 15, 2021 at 10:05:47AM +0800, Lu Baolu wrote: > The vfio needs to set DMA_OWNER_USER for the entire group when attaching
The vfio subsystem? driver?
> it to a vfio container. So expose group variants of setting/releasing dma > ownership for this purpose. > > This also exposes the helper iommu_group_dma_owner_unclaimed() for vfio > report to userspace if the group is viable to user assignment, for
.. for vfio to report .. ?
> void iommu_device_release_dma_owner(struct device *dev, enum iommu_dma_owner owner); > +int iommu_group_set_dma_owner(struct iommu_group *group, enum iommu_dma_owner owner, > + struct file *user_file); > +void iommu_group_release_dma_owner(struct iommu_group *group, enum iommu_dma_owner owner);
Pleae avoid all these overly long lines.
> +static inline int iommu_group_set_dma_owner(struct iommu_group *group, > + enum iommu_dma_owner owner, > + struct file *user_file) > +{ > + return -EINVAL; > +} > + > +static inline void iommu_group_release_dma_owner(struct iommu_group *group, > + enum iommu_dma_owner owner) > +{ > +} > + > +static inline bool iommu_group_dma_owner_unclaimed(struct iommu_group *group) > +{ > + return false; > +}
Why do we need these stubs? All potential callers should already require CONFIG_IOMMU_API? Same for the helpers added in patch 1, btw.
> + mutex_lock(&group->mutex); > + ret = __iommu_group_set_dma_owner(group, owner, user_file); > + mutex_unlock(&group->mutex);
> + mutex_lock(&group->mutex); > + __iommu_group_release_dma_owner(group, owner); > + mutex_unlock(&group->mutex);
Unless I'm missing something (just skipping over the patches), the existing callers also take the lock just around these calls, so we don't really need the __-prefixed lowlevel helpers.
> + mutex_lock(&group->mutex); > + owner = group->dma_owner; > + mutex_unlock(&group->mutex);
No need for a lock to read a single scalar.
> + > + return owner == DMA_OWNER_NONE; > +} > +EXPORT_SYMBOL_GPL(iommu_group_dma_owner_unclaimed);
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