On Tue, Feb 11, 2025 at 02:16:20PM -0400, Jason Gunthorpe wrote:
> On Sat, Feb 08, 2025 at 01:02:39AM -0800, Nicolin Chen wrote:
>
> > +static struct iommufd_attach_handle *
> > +iommu_group_get_iommufd_handle(struct iommu_group *group)
> > +{
> > + struct iommu_attach_handle *handle;
> > +
> > + handle = iommu_attach_handle_get(group, IOMMU_NO_PASID, 0);
> > + if (IS_ERR(handle))
> > + return NULL;
> > + return to_iommufd_handle(handle);
> > +}
> > +
> > +/*
> > + * Called by the irq code if the platform translates the MSI address through the
> > + * IOMMU. msi_addr is the physical address of the MSI page. iommufd will
> > + * allocate a fd global iova for the physical page that is the same on all
> > + * domains and devices.
> > + */
> > +#ifdef CONFIG_IRQ_MSI_IOMMU
> > +int iommufd_sw_msi(struct iommu_domain *domain, struct msi_desc *desc,
> > + phys_addr_t msi_addr)
> > +{
> > + struct device *dev = msi_desc_to_dev(desc);
> > + struct iommufd_hwpt_paging *hwpt_paging;
> > + struct iommufd_attach_handle *handle;
> > + struct iommufd_sw_msi_map *msi_map;
> > + struct iommufd_ctx *ictx;
> > + unsigned long iova;
> > + int rc;
> > +
> > + handle = iommu_group_get_iommufd_handle(dev->iommu_group);
> > + if (!handle)
> > + return 0;
>
> I think you should open code this and leave the other function
> alone. The locking rules are different here.
>
> iommufd_device_get_attach_handle() should be locked under the
> igroup->lock
>
> While in this context we are locked under the iommu core group mutex.
>
> A comment will help
>
> /*
> * It is safe to call iommu_attach_handle_get() here because the iommu
> * core code invokes this under the group mutex which also prevents any
> * change of the attach handle for the duration of this function.
> */
> iommu_group_mutex_assert(dev);
Ack. I reverted that part and added this piece.
Thanks
Nicolin
