RE: [PATCH v2 4/6] iommufd: Deliver fault messages to user space

[Shameerali Kolothum Thodi]

> -----Original Message-----
> From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Sent: Thursday, October 26, 2023 3:49 AM
> To: Jason Gunthorpe <jgg@xxxxxxxx>; Kevin Tian <kevin.tian@xxxxxxxxx>; Joerg
> Roedel <joro@xxxxxxxxxx>; Will Deacon <will@xxxxxxxxxx>; Robin Murphy
> <robin.murphy@xxxxxxx>; Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>;
> Nicolin Chen <nicolinc@xxxxxxxxxx>; Yi Liu <yi.l.liu@xxxxxxxxx>; Jacob Pan
> <jacob.jun.pan@xxxxxxxxxxxxxxx>
> Cc: iommu@xxxxxxxxxxxxxxx; linux-kselftest@xxxxxxxxxxxxxxx;
> virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Lu
> Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Subject: [PATCH v2 4/6] iommufd: Deliver fault messages to user space
> 
[...]

Hi,

> +static ssize_t hwpt_fault_fops_write(struct file *filep,
> +				     const char __user *buf,
> +				     size_t count, loff_t *ppos)
> +{
> +	size_t response_size = sizeof(struct iommu_hwpt_page_response);
> +	struct hw_pgtable_fault *fault = filep->private_data;
> +	struct iommu_hwpt_page_response response;
> +	struct iommufd_hw_pagetable *hwpt;
> +	struct iopf_group *iter, *group;
> +	struct iommufd_device *idev;
> +	size_t done = 0;
> +	int rc = 0;
> +
> +	if (*ppos || count % response_size)
> +		return -ESPIPE;
> +
> +	mutex_lock(&fault->mutex);
> +	while (!list_empty(&fault->response) && count > done) {
> +		rc = copy_from_user(&response, buf + done, response_size);
> +		if (rc)
> +			break;
> +
> +		/* Get the device that this response targets at. */
> +		idev = container_of(iommufd_get_object(fault->ictx,
> +						       response.dev_id,
> +						       IOMMUFD_OBJ_DEVICE),
> +				    struct iommufd_device, obj);
> +		if (IS_ERR(idev)) {
> +			rc = PTR_ERR(idev);
> +			break;
> +		}
> +
> +		/*
> +		 * Get the hw page table that this response was generated for.
> +		 * It must match the one stored in the fault data.
> +		 */
> +		hwpt = container_of(iommufd_get_object(fault->ictx,
> +						       response.hwpt_id,
> +
> IOMMUFD_OBJ_HW_PAGETABLE),
> +				    struct iommufd_hw_pagetable, obj);
> +		if (IS_ERR(hwpt)) {
> +			iommufd_put_object(&idev->obj);
> +			rc = PTR_ERR(hwpt);
> +			break;
> +		}
> +
> +		if (hwpt != fault->hwpt) {
> +			rc = -EINVAL;
> +			goto put_obj;
> +		}
> +
> +		group = NULL;
> +		list_for_each_entry(iter, &fault->response, node) {
> +			if (response.grpid != iter->last_fault.fault.prm.grpid)
> +				continue;
> +
> +			if (idev->dev != iter->dev)
> +				continue;
> +
> +			if ((iter->last_fault.fault.prm.flags &
> +			     IOMMU_FAULT_PAGE_REQUEST_PASID_VALID) &&
> +			    response.pasid != iter->last_fault.fault.prm.pasid)
> +				continue;

I am trying to get vSVA working with this series and got hit by the above check.
On ARM platforms, page responses to stall events(CMD_RESUME) do not have
an associated pasid.  I think, either we need to check here using
IOMMU_FAULT_PAGE_RESPONSE_NEEDS_PASID or remove the check 
as it will be eventually done in iommu_page_response(). 

Thanks,
Shameer