Messages in this thread | | | Date | Tue, 9 Mar 2021 12:47:43 -0400 | From | Jason Gunthorpe <> | Subject | Re: [PATCH v1 07/14] vfio: Add a device notifier interface |
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On Tue, Mar 09, 2021 at 08:45:13AM -0700, Alex Williamson wrote:
> > I'm having trouble guessing why we need to refcount the group to add a > > notifier to the device's notifier chain? > > > > I suppose it actually has to do with the MMIO mapping? But I don't > > know what the relation is between MMIO mappings in the IOMMU and the > > container? This could deserve a comment? > > Sure, I can add a comment. We want to make sure the device remains > within an IOMMU context so long as we have a DMA mapping to the device > MMIO, which could potentially manipulate the device. IOMMU context is > managed a the group level.
I find refcounting is easier to understand if the refcount inc/dec is near the thing that is actually using the object - so I'd suggest to move this to the iommu code.
A comment sounds like a good idea since this is security sensitive
Jason
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