Messages in this thread | | | Subject | Re: [PATCH v11 05/10] iommu/vt-d: Add bind guest PASID support | From | Auger Eric <> | Date | Fri, 17 Apr 2020 09:46:55 +0200 |
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Hi Kevin, On 4/17/20 4:45 AM, Tian, Kevin wrote: >> 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. Ah OK. So if we can detect the case here it is even better
Thanks
Eric > >> >> 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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