Messages in this thread | | | Subject | Re: [RFC PATCH] iommu/vt-d: Fix IOMMU field not populated on device hot re-plug | From | Lu Baolu <> | Date | Thu, 29 Aug 2019 17:08:18 +0800 |
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Hi,
On 8/29/19 3:58 PM, Janusz Krzysztofik wrote: > Hi Baolu, > > On Thursday, August 29, 2019 3:43:31 AM CEST Lu Baolu wrote: >> 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 users that their active DMA mappings are no longer valid and they 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? > > Device core calls BUS_NOTIFY_UNBOUND_DRIVER on each driver unbind, regardless > of a device being removed or not. As long as the device is not unplugged and > the BUS_NOTIFY_REMOVED_DEVICE notification not generated, an unbound driver is > not a problem here. > Morever, BUS_NOTIFY_UNBOUND_DRIVER is called even before > BUS_NOTIFY_REMOVED_DEVICE so that wouldn't help anyway. > Last but not least, bus events are independent of the IOMMU driver use via > DMA-API it exposes.
Fair enough.
> > If keeping data for unplugged devices and reusing it on device re-plug is not > acceptable then maybe the IOMMU driver should perform reference counting of > its internal resources occupied by DMA-API users and perform cleanups on last > release?
I am not saying that keeping data is not acceptable. I just want to check whether there are any other solutions.
Best regards, Baolu
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