Re: [PATCH v9 12/21] iommufd/device: Add pasid_attach array to track per-PASID attach

[Yi Liu <yi.l.liu@intel.com>]

On 2025/3/13 20:35, Yi Liu wrote:
> PASIDs of PASID-capable device can be attached to hwpt separately, hence
> a pasid array to track per-PASID attachment is necessary. The index
> IOMMU_NO_PASID is used by the RID path. Hence drop the igroup->handle.
> 
> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> ---
>   drivers/iommu/iommufd/device.c          | 78 +++++++++++++++++--------
>   drivers/iommu/iommufd/iommufd_private.h |  4 +-
>   2 files changed, 54 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
> index 7d52f304b9bb..63b189a5b8ac 100644
> --- a/drivers/iommu/iommufd/device.c
> +++ b/drivers/iommu/iommufd/device.c
> @@ -23,7 +23,7 @@ static void iommufd_group_release(struct kref *kref)
>   	struct iommufd_group *igroup =
>   		container_of(kref, struct iommufd_group, ref);
>   
> -	WARN_ON(igroup->handle);
> +	WARN_ON(!xa_empty(&igroup->pasid_attach));
>   
>   	xa_cmpxchg(&igroup->ictx->groups, iommu_group_id(igroup->group), igroup,
>   		   NULL, GFP_KERNEL);
> @@ -90,6 +90,7 @@ static struct iommufd_group *iommufd_get_group(struct iommufd_ctx *ictx,
>   
>   	kref_init(&new_igroup->ref);
>   	mutex_init(&new_igroup->lock);
> +	xa_init(&new_igroup->pasid_attach);
>   	new_igroup->sw_msi_start = PHYS_ADDR_MAX;
>   	/* group reference moves into new_igroup */
>   	new_igroup->group = group;
> @@ -293,16 +294,19 @@ u32 iommufd_device_to_id(struct iommufd_device *idev)
>   }
>   EXPORT_SYMBOL_NS_GPL(iommufd_device_to_id, "IOMMUFD");
>   
> -static int iommufd_group_device_num(struct iommufd_group *igroup)
> +static int iommufd_group_device_num(struct iommufd_group *igroup,
> +				    ioasid_t pasid)
>   {
> +	struct iommufd_attach_handle *handle;
>   	struct iommufd_device *idev;
>   	unsigned long index;
>   	int count = 0;
>   
>   	lockdep_assert_held(&igroup->lock);
>   
> -	if (igroup->handle)
> -		xa_for_each(&igroup->handle->device_array, index, idev)
> +	handle = xa_load(&igroup->pasid_attach, pasid);
> +	if (handle)
> +		xa_for_each(&handle->device_array, index, idev)
>   			count++;
>   	return count;
>   }
> @@ -472,7 +476,7 @@ iommufd_device_attach_reserved_iova(struct iommufd_device *idev,
>   	if (rc)
>   		return rc;
>   
> -	if (!igroup->handle) {
> +	if (!xa_load(&igroup->pasid_attach, IOMMU_NO_PASID)) {
>   		rc = iommufd_group_setup_msi(igroup, hwpt_paging);
>   		if (rc) {
>   			iopt_remove_reserved_iova(&hwpt_paging->ioas->iopt,
> @@ -485,10 +489,14 @@ iommufd_device_attach_reserved_iova(struct iommufd_device *idev,
>   
>   /* The device attach/detach/replace helpers for attach_handle */
>   
> -static bool iommufd_device_is_attached(struct iommufd_device *idev)
> +static bool iommufd_device_is_attached(struct iommufd_device *idev,
> +				       ioasid_t pasid)
>   {
> -	WARN_ON(!idev->igroup->handle);
> -	return xa_load(&idev->igroup->handle->device_array, idev->obj.id);
> +	struct iommufd_attach_handle *handle;
> +
> +	handle = xa_load(&idev->igroup->pasid_attach, pasid);
> +	WARN_ON(!handle);
> +	return xa_load(&handle->device_array, idev->obj.id);
>   }
>   
>   static int iommufd_hwpt_attach_device(struct iommufd_hw_pagetable *hwpt,
> @@ -574,19 +582,25 @@ int iommufd_hw_pagetable_attach(struct iommufd_hw_pagetable *hwpt,
>   {
>   	struct iommufd_hwpt_paging *hwpt_paging = find_hwpt_paging(hwpt);
>   	bool attach_resv = hwpt_paging && pasid == IOMMU_NO_PASID;
> +	struct iommufd_hw_pagetable *old_hwpt = NULL;
>   	struct iommufd_group *igroup = idev->igroup;
> -	struct iommufd_hw_pagetable *old_hwpt;
>   	struct iommufd_attach_handle *handle;
>   	int rc;
>   
>   	mutex_lock(&igroup->lock);
>   
> -	handle = igroup->handle;
> +	handle = xa_cmpxchg(&igroup->pasid_attach, pasid, NULL,
> +			    XA_ZERO_ENTRY, GFP_KERNEL);
> +	if (xa_is_err(handle)) {
> +		rc = PTR_ERR(handle);

An issue was reported by Dan. This should be rc = xa_err(handle); Feel free
to let me know if a v10 is necessary to fix this.

https://lore.kernel.org/all/202503161104.CANtg5Ng-lkp@intel.com/

Regards,
Yi Liu