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From: Will Deacon <will@kernel.org>
To: Joerg Roedel <joro@8bytes.org>
Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
	Robin Murphy <robin.murphy@arm.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Subject: Re: [PATCH 5/7] iommu/arm-smmu-v3: Allow building as a module
Date: Fri, 8 Nov 2019 11:03:10 +0000	[thread overview]
Message-ID: <20191108110310.GC19153@willie-the-truck> (raw)
In-Reply-To: <20191105121508.GA3479@8bytes.org>

Hi Joerg,

On Tue, Nov 05, 2019 at 01:15:08PM +0100, Joerg Roedel wrote:
> On Thu, Oct 31, 2019 at 03:42:47PM +0000, Will Deacon wrote:
> > Generally, I think unloading the IOMMU driver module while there are
> > active users is a pretty bad idea, much like unbinding the driver via
> > /sys in the same situation would also be fairly daft. However, I *think*
> > the code in __device_release_driver() tries to deal with this by
> > iterating over the active consumers and ->remove()ing them first.
> > 
> > I'm without hardware access at the moment, so I haven't been able to
> > test this myself. We could nobble the module_exit() hook, but there's
> > still the "force unload" option depending on the .config.
> 
> Okay, but besides the force-unload case, can we prevent accidential
> unloading by taking a reference to the module in add_device() and release
> it in remove_device()?

That's probably a sensible starting point, yes. In conjunction with the
patch from Jean-Philippe to introduce bus_unset_iommu(), we might have
a fighting chance of getting this to work.

I'll spin a v2.

Thanks!

Will

  reply	other threads:[~2019-11-08 11:03 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-30 14:51 [PATCH 0/7] iommu: Permit modular builds of ARM SMMU[v3] drivers Will Deacon
2019-10-30 14:51 ` [PATCH 1/7] drivers/iommu: Export core IOMMU API symbols to permit modular drivers Will Deacon
2019-10-30 14:51 ` [PATCH 2/7] iommu/of: Request ACS from the PCI core when configuring IOMMU linkage Will Deacon
2019-10-30 14:51 ` [PATCH 3/7] PCI: Export pci_ats_disabled() as a GPL symbol to modules Will Deacon
2019-10-30 20:30   ` Bjorn Helgaas
2019-10-30 14:51 ` [PATCH 4/7] Revert "iommu/arm-smmu: Make arm-smmu-v3 explicitly non-modular" Will Deacon
2019-10-30 14:51 ` [PATCH 5/7] iommu/arm-smmu-v3: Allow building as a module Will Deacon
2019-10-30 19:31   ` Joerg Roedel
2019-10-31 15:42     ` Will Deacon
2019-11-04 19:15       ` Jean-Philippe Brucker
2019-11-08 14:54         ` Will Deacon
2019-11-05 12:15       ` Joerg Roedel
2019-11-08 11:03         ` Will Deacon [this message]
2019-10-30 14:51 ` [PATCH 6/7] Revert "iommu/arm-smmu: Make arm-smmu explicitly non-modular" Will Deacon
2019-10-30 23:09   ` Jordan Crouse
2019-10-31 12:03     ` Will Deacon
2019-10-31 15:32       ` Jordan Crouse
2019-10-30 14:51 ` [PATCH 7/7] iommu/arm-smmu: Allow building as a module Will Deacon
2019-10-30 15:22   ` Rob Herring
2019-10-30 15:26     ` Will Deacon
2019-10-30 15:33     ` Robin Murphy
2019-11-04 19:34   ` Isaac J. Manjarres
2019-11-07 12:48     ` Will Deacon
2019-10-30 15:35 ` [PATCH 0/7] iommu: Permit modular builds of ARM SMMU[v3] drivers Robin Murphy
2019-10-30 15:54   ` Will Deacon
2019-10-31  0:57     ` Saravana Kannan
2019-10-31 19:37       ` Jean-Philippe Brucker
2019-10-31 23:34         ` Saravana Kannan
2019-11-01 10:27           ` John Garry
2019-11-01 21:13             ` Saravana Kannan
2019-11-04 12:16               ` John Garry
2019-11-04 13:29                 ` Robin Murphy
2019-11-07  6:11                   ` Saravana Kannan
2019-11-07  9:13                     ` Jean-Philippe Brucker
2019-11-07  6:02                 ` Saravana Kannan
2019-11-01 11:41           ` Jean-Philippe Brucker
2019-11-01 12:28             ` Lorenzo Pieralisi
2019-11-01 21:26               ` Saravana Kannan
2019-11-04 11:43                 ` Lorenzo Pieralisi
2019-11-07  5:55                   ` Saravana Kannan
2019-11-01 17:21         ` Will Deacon
2019-11-04  7:54           ` Jean-Philippe Brucker
2019-11-07  6:16       ` Saravana Kannan

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