From: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
"David Woodhouse" <dwmw2@infradead.org>,
intel-gfx@lists.freedesktop.org,
"Michał Wajdeczko" <michal.wajdeczko@intel.com>
Subject: Re: [RFC PATCH] iommu/vt-d: Fix IOMMU field not populated on device hot re-plug
Date: Thu, 29 Aug 2019 09:58:05 +0200 [thread overview]
Message-ID: <3255251.C7nBVfOIaa@jkrzyszt-desk.ger.corp.intel.com> (raw)
In-Reply-To: <0cf4e930-1132-1e7f-815b-57a08a1fe5de@linux.intel.com>
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 users that their active DMA mappings are no longer valid and they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.
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?
Thanks,
Janusz
> > Thanks,
> > Janusz
>
> Best regards,
> Baolu
>
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next prev parent reply other threads:[~2019-08-29 7:58 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-22 14:29 [RFC PATCH] iommu/vt-d: Fix IOMMU field not populated on device hot re-plug Janusz Krzysztofik
2019-08-23 1:51 ` Lu Baolu
2019-08-26 8:15 ` Janusz Krzysztofik
2019-08-26 8:29 ` Lu Baolu
2019-08-27 9:35 ` Janusz Krzysztofik
2019-08-28 0:56 ` Lu Baolu
2019-08-28 14:17 ` Janusz Krzysztofik
2019-08-29 1:43 ` Lu Baolu
2019-08-29 7:58 ` Janusz Krzysztofik [this message]
2019-08-29 9:08 ` Lu Baolu
2019-09-02 8:37 ` Janusz Krzysztofik
2019-09-03 1:29 ` Lu Baolu
2019-09-03 7:41 ` Janusz Krzysztofik
2019-10-01 15:01 ` Janusz Krzysztofik
2019-10-08 2:27 ` Lu Baolu
2019-10-11 6:54 ` Lu Baolu
2019-10-11 10:27 ` Janusz Krzysztofik
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