Messages in this thread | | | From | "Tian, Kevin" <> | Subject | RE: [PATCH v11 05/10] iommu/vt-d: Add bind guest PASID support | Date | Fri, 17 Apr 2020 02:45:22 +0000 |
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> From: Auger Eric > Sent: Thursday, April 16, 2020 6:43 PM > [...] > >>> + if (svm) { > >>> + /* > >>> + * If we found svm for the PASID, there must be at > >>> + * least one device bond, otherwise svm should be > >>> freed. > >>> + */ > >>> + if (WARN_ON(list_empty(&svm->devs))) { > >>> + ret = -EINVAL; > >>> + goto out; > >>> + } > >>> + > >>> + for_each_svm_dev(sdev, 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++; > >> What if this is not an mdev device. Is it also allowed? > > Yes. IOMMU and VT-d driver is not mdev aware. Here mdev is just an > > example of normal use case. You can bind the same PCI device (PF or > > SRIOV VF) more than once to the same PASID. Just need to unbind also. > > I don't get the point of binding a non mdev device several times with > the same PASID. Do you intend to allow that at userspace level or > prevent this from happening in VFIO?
I feel it's better to prevent this from happening, otherwise VFIO also needs to track the bind count and do multiple unbinds at mm_exit. But it's not necessary to prevent it in VFIO. We can check here upon whether aux_domain is valid, and if not return -EBUSY.
> > Besides, the comment is a bit misleading as it gives the impression it > is only true for mdev and there is no associated check.
Thanks Kevin
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