Re: [PATCH v5 5/9] iommufd: Add iommufd fault object

Baolu Lu
2024-05-10T09:13:34Z

On 2024/5/8 8:22, Jason Gunthorpe wrote:
> On Tue, Apr 30, 2024 at 10:57:06PM +0800, Lu Baolu wrote:
>> +static ssize_t iommufd_fault_fops_read(struct file *filep, char __user *buf,
>> + size_t count, loff_t *ppos)
>> +{
>> + size_t fault_size = sizeof(struct iommu_hwpt_pgfault);
>> + struct iommufd_fault *fault = filep->private_data;
>> + struct iommu_hwpt_pgfault data;
>> + struct iommufd_device *idev;
>> + struct iopf_group *group;
>> + struct iopf_fault *iopf;
>> + size_t done = 0;
>> + int rc;
>> +
>> + if (*ppos || count % fault_size)
>> + return -ESPIPE;
>> +
>> + mutex_lock(&fault->mutex);
>> + while (!list_empty(&fault->deliver) && count > done) {
>> + group = list_first_entry(&fault->deliver,
>> + struct iopf_group, node);
>> +
>> + if (list_count_nodes(&group->faults) * fault_size > count - done)
>> + break;
>
> Can this list_count be precomputed when we build the fault group?

Yes. Done.

>
>> +
>> + idev = group->attach_handle->idev;
>> + if (!idev)
>> + break;
>
> This check should be done before adding the fault to the linked
> list. See my other note about the race.

Done.

>
>> +
>> + rc = xa_alloc(&idev->faults, &group->cookie, group,
>> + xa_limit_32b, GFP_KERNEL);
>> + if (rc)
>> + break;
>
> This error handling is not quite right, if done == 0 then this should
> return rc.
>
>
>> +
>> + list_for_each_entry(iopf, &group->faults, list) {
>> + iommufd_compose_fault_message(&iopf->fault,
>> + &data, idev,
>> + group->cookie);
>> + rc = copy_to_user(buf + done, &data, fault_size);
>> + if (rc) {
>> + xa_erase(&idev->faults, group->cookie);
>> + break;
>
> Same here
>
> (same comment on the write side too)

All fixed. Thank you!

Best regards,
baolu