Re: [RFC PATCH] iommu/vt-d: Fix IOMMU field not populated on device hot re-plug

[Lu Baolu]

Hi Janusz,

On 8/28/19 10:17 PM, Janusz Krzysztofik wrote:
> > We should avoid kernel panic when a intel_unmap() is called against
> > a non-existent domain.
> Does that mean you suggest to replace
> 	BUG_ON(!domain);
> with something like
> 	if (WARN_ON(!domain))
> 		return;
> and to not care of orphaned mappings left allocated?  Is there a way to inform
> users that their active DMA mappings are no longer valid and they shouldn't
> call dma_unmap_*()?
>
> > But we shouldn't expect the IOMMU driver not
> > cleaning up the domain info when a device remove notification comes and
> > wait until all file descriptors being closed, right?
> Shouldn't then the IOMMU driver take care of cleaning up resources still
> allocated on device remove before it invalidates and forgets their pointers?

You are right. We need to wait until all allocated resources (iova and
mappings) to be released.

How about registering a callback for BUS_NOTIFY_UNBOUND_DRIVER, and
removing the domain info when the driver detachment completes?

> Thanks,
> Janusz

Best regards,
Baolu