Re: [XEN][PATCH v10 12/20] xen/smmu: Add remove_device callback for smmu_iommu ops

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 29 Aug 2023, Michal Orzel wrote:
> On 25/08/2023 10:02, Vikram Garhwal wrote:
> > Add remove_device callback for removing the device entry from smmu-master 
> > using
> > following steps:
> > 1. Find if SMMU master exists for the device node.
> > 2. Check if device is currently in use.
> Since you removed a call to iommu_dt_device_is_assigned_locked(), you do not 
> check it from SMMU, right?
> You are relying on a check done in iommu_remove_dt_device().
> This wants to be mentioned. However, Julien suggested to do the check for 
> internal SMMU state.
> Looking at the code, when the device is assigned, we do:
> dev_iommu_domain(dev) = domain;
> and when de-assigned:
> dev_iommu_domain(dev) = NULL;
> 
> This means that before calling remove_smmu_master() you could do:
> 
> /* Make sure device is not assigned */
> if (dev_iommu_domain(dev))
>     return -EBUSY;
> 
> @Julien, @Stefano?

I think it is OK without it, as we have a call to
iommu_dt_device_is_assigned_locked(np) already in
iommu_remove_dt_device?