Re: [PATCH v4 20/22] iommu/vt-d: Add bind guest PASID support

[Jacob Pan <jacob.jun.pan@linux.intel.com>]

On Fri, 5 Jul 2019 10:21:27 +0800
Lu Baolu <baolu.lu@linux.intel.com> wrote:

> Hi Jacob,
> 
> On 6/28/19 4:22 AM, Jacob Pan wrote:
> >>> +		}
> >>> +		refcount_set(&svm->refs, 0);
> >>> +		ioasid_set_data(data->hpasid, svm);
> >>> +		INIT_LIST_HEAD_RCU(&svm->devs);
> >>> +		INIT_LIST_HEAD(&svm->list);
> >>> +
> >>> +		mmput(svm->mm);
> >>> +	}
> >>> +	sdev = kzalloc(sizeof(*sdev), GFP_KERNEL);
> >>> +	if (!sdev) {
> >>> +		ret = -ENOMEM;
> >>> +		goto out;  
> >> I think you need to clean up svm if its device list is empty here,
> >> as you said above:
> >>  
> > No, we come here only if the device list is not empty and the new
> > device to bind is different than any existing device in the list.
> > If we cannot allocate memory for the new device, should not free
> > the existing SVM, right?
> >   
> 
> I'm sorry, but the code doesn't show this. We come here even an svm
> data structure was newly created with an empty device list. I post
> the code below to ensure that we are reading a same piece of code.
> 
Sorry for the delay. You are right, I need to clean up svm if device
list is empty.

Thanks!
>          mutex_lock(&pasid_mutex);
>          svm = ioasid_find(NULL, data->hpasid, NULL);
>          if (IS_ERR(svm)) {
>                  ret = PTR_ERR(svm);
>                  goto out;
>          }
>          if (svm) {
>                  /*
>                   * If we found svm for the PASID, there must be at
>                   * least one device bond, otherwise svm should be
> freed. */
>                  BUG_ON(list_empty(&svm->devs));
> 
>                  for_each_svm_dev() {
>                          /* In case of multiple sub-devices of the
> same pdev assigned, we should
>                           * allow multiple bind calls with the same 
> PASID and pdev.
>                           */
>                          sdev->users++;
>                          goto out;
>                  }
>          } else {
>                  /* We come here when PASID has never been bond to a 
> device. */
>                  svm = kzalloc(sizeof(*svm), GFP_KERNEL);
>                  if (!svm) {
>                          ret = -ENOMEM;
>                          goto out;
>                  }
>                  /* REVISIT: upper layer/VFIO can track host process 
> that bind the PASID.
>                   * ioasid_set = mm might be sufficient for vfio to 
> check pasid VMM
>                   * ownership.
>                   */
>                  svm->mm = get_task_mm(current);
>                  svm->pasid = data->hpasid;
>                  if (data->flags & IOMMU_SVA_GPASID_VAL) {
>                          svm->gpasid = data->gpasid;
>                          svm->flags &= SVM_FLAG_GUEST_PASID;
>                  }
>                  refcount_set(&svm->refs, 0);
>                  ioasid_set_data(data->hpasid, svm);
>                  INIT_LIST_HEAD_RCU(&svm->devs);
>                  INIT_LIST_HEAD(&svm->list);
> 
>                  mmput(svm->mm);
>          }
>          sdev = kzalloc(sizeof(*sdev), GFP_KERNEL);
>          if (!sdev) {
>                  ret = -ENOMEM;
>                  goto out;
>          }
>          sdev->dev = dev;
>          sdev->users = 1;
> 
> Best regards,
> Baolu

[Jacob Pan]