From: Sakari Ailus <sakari.ailus@iki.fi>
To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: okaya@codeaurora.org,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
linux-arm-msm@vger.kernel.org, Joerg Roedel <joro@8bytes.org>,
Magnus Damm <magnus.damm@gmail.com>,
Robin Murphy <robin.murphy@arm.com>,
Will Deacon <will.deacon@arm.com>,
Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
iommu@lists.linux-foundation.org,
Geert Uytterhoeven <geert@linux-m68k.org>,
Hanjun Guo <hanjun.guo@linaro.org>,
linux-pci <linux-pci@vger.kernel.org>,
Bjorn Helgaas <bhelgaas@google.com>,
tn@semihalf.com, sricharan@codeaurora.org,
linux-arm-msm-owner@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Marek Szyprowski <m.szyprowski@samsung.com>
Subject: Re: [PATCH V8 07/11] iommu: of: Handle IOMMU lookup failure with deferred probing or error
Date: Tue, 16 May 2017 12:47:32 +0300 [thread overview]
Message-ID: <20170516094732.GM3227@valkosipuli.retiisi.org.uk> (raw)
In-Reply-To: <1924197.MWBQ7kvoOo@avalon>
Hi Laurent,
On Tue, May 16, 2017 at 10:17:08AM +0300, Laurent Pinchart wrote:
> Hi Sricharan,
>
> On Tuesday 16 May 2017 07:53:57 sricharan@codeaurora.org wrote:
> > On 2017-05-16 03:04, Laurent Pinchart wrote:
> > > On Monday 15 May 2017 23:37:16 Laurent Pinchart wrote:
> > >> On Wednesday 03 May 2017 15:54:59 Sricharan R wrote:
> > >>> On 5/3/2017 3:24 PM, Robin Murphy wrote:
> > >>>> On 02/05/17 19:35, Geert Uytterhoeven wrote:
> > >>>>> On Fri, Feb 3, 2017 at 4:48 PM, Sricharan R wrote:
> > >>>>>> From: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> > >>>>>>
> > >>>>>> Failures to look up an IOMMU when parsing the DT iommus property
> > >>>>>> need to be handled separately from the .of_xlate() failures to
> > >>>>>> support deferred probing.
> > >>>>>>
> > >>>>>> The lack of a registered IOMMU can be caused by the lack of a driver
> > >>>>>> for the IOMMU, the IOMMU device probe not having been performed yet,
> > >>>>>> having been deferred, or having failed.
> > >>>>>>
> > >>>>>> The first case occurs when the device tree describes the bus master
> > >>>>>> and IOMMU topology correctly but no device driver exists for the
> > >>>>>> IOMMU yet or the device driver has not been compiled in. Return NULL,
> > >>>>>> the caller will configure the device without an IOMMU.
> > >>>>>>
> > >>>>>> The second and third cases are handled by deferring the probe of the
> > >>>>>> bus master device which will eventually get reprobed after the
> > >>>>>> IOMMU.
> > >>>>>>
> > >>>>>> The last case is currently handled by deferring the probe of the bus
> > >>>>>> master device as well. A mechanism to either configure the bus
> > >>>>>> master device without an IOMMU or to fail the bus master device probe
> > >>>>>> depending on whether the IOMMU is optional or mandatory would be a
> > >>>>>> good enhancement.
> > >>>>>>
> > >>>>>> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> > >>>>>> Signed-off-by: Laurent Pichart
> > >>>>>> <laurent.pinchart+renesas@ideasonboard.com>
> > >>>>>> Signed-off-by: Sricharan R <sricharan@codeaurora.org>
> > >>>>>
> > >>>>> This patch broke Renesas R-Car Gen3 platforms in renesas-drivers.
> > >>>>> As the IOMMU nodes in DT are not yet enabled, all devices having
> > >>>>> iommus properties in DT now fail to probe.
> > >>>>
> > >>>> How exactly do they fail to probe? Per d7b0558230e4, if there are no
> > >>>> ops registered then they should merely defer until we reach the point
> > >>>> of giving up and ignoring the IOMMU. Is it just that you have no other
> > >>>> late-probing drivers or post-init module loads to kick the deferred
> > >>>> queue after that point? I did try to find a way to explicitly kick it
> > >>>> from a suitably late initcall, but there didn't seem to be any obvious
> > >>>> public interface - anyone have any suggestions?
> > >>>>
> > >>>> I think that's more of a general problem with the probe deferral
> > >>>> mechanism itself (I've seen the same thing happen with some of the
> > >>>> CoreSight stuff on Juno due to the number of inter-component
> > >>>> dependencies) rather than any specific fault of this series.
> > >>>
> > >>> I was thinking of an additional check like below to avoid the
> > >>> situation ?
> > >>>
> > >>> From 499b6e662f60f23740b8880882b0a16f16434501 Mon Sep 17 00:00:00 2001
> > >>> From: Sricharan R <sricharan@codeaurora.org>
> > >>> Date: Wed, 3 May 2017 13:16:59 +0530
> > >>> Subject: [PATCH] iommu: of: Fix check for returning EPROBE_DEFER
> > >>>
> > >>> While returning EPROBE_DEFER for iommu masters
> > >>> take in to account of iommu nodes that could be
> > >>> marked in DT as 'status=disabled', in which case
> > >>> simply return NULL and let the master's probe
> > >>> continue rather than deferring.
> > >>>
> > >>> Signed-off-by: Sricharan R <sricharan@codeaurora.org>
> > >>> ---
> > >>>
> > >>> drivers/iommu/of_iommu.c | 1 +
> > >>> 1 file changed, 1 insertion(+)
> > >>>
> > >>> diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
> > >>> index 9f44ee8..e6e9bec 100644
> > >>> --- a/drivers/iommu/of_iommu.c
> > >>> +++ b/drivers/iommu/of_iommu.c
> > >>> @@ -118,6 +118,7 @@ static bool of_iommu_driver_present(struct
> > >>> device_node *np)
> > >>>
> > >>> ops = iommu_ops_from_fwnode(fwnode);
> > >>> if ((ops && !ops->of_xlate) ||
> > >>> + !of_device_is_available(iommu_spec->np) ||
> > >>> (!ops && !of_iommu_driver_present(iommu_spec->np)))
> > >>> return NULL;
> > >>
> > >> This looks good to me, but won't be enough. The ipmmu-vmsa driver in
> > >> v4.12-rc1 doesn't call iommu_device_register() and thus won't be found
> > >> by iommu_ops_from_fwnode(). Furthermore, it doesn't IOMMU_OF_DECLARE(),
> > >> and thus will always be considered as absent.
> > >>
> > >> I agree that the ipmmu-vmsa driver needs to be fixed, but it would
> > >> have been nice to check existing IOMMU drivers before merging this patch
> > >> series...
> > >
> > > Please pardon the question, but has this patch series been tested on
> > > ARM32 ?
> > >
> > > When the device is probed the arch_setup_dma_ops() function is called.
> > > It sets the device's dma_ops and the mapping (in
> > > __arm_iommu_attach_device()). If probe is deferred,
> > > arch_teardown_dma_ops() is called which in turn calls
> > > arch_teardown_dma_ops(). This removes the mapping but doesn't touch the
> > > dma_ops. The next time the device is probed, arch_setup_dma_ops() bails
> > > out immediately as the dma_ops are already set, leaving us with a device
> > > bound to IOMMU operations but with no mapping. This oopses later as soon
> > > as the kernel tries to map memory for the device through the IOMMU.
> >
> > Resetting the dma_ops for arm32 was added in this patch [1], which I
> > missed to send in the original series, but now have added to Russell's patch
> > tracking system.
>
> Thank you. I fear that won't be enough though.
>
> > [1] https://patchwork.kernel.org/patch/9434105/
>
> Quoting the patch:
>
> > arch_teardown_dma_ops() being the inverse of arch_setup_dma_ops()
> > ,dma_ops should be cleared in the teardown path. Otherwise
> > this causes problem when the probe of device is retried after
> > being deferred. The device's iommu structures are cleared
> > after EPROBEDEFER error, but on the next try dma_ops will still
> > be set to old value, which is not right.
> >
> > Signed-off-by: Sricharan R <sricharan@codeaurora.org>
> > Reviewed-by: Robin Murphy <robin.murphy@arm.com>
> > ---
> > arch/arm/mm/dma-mapping.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> > index ab4f745..a40f03e 100644
> > --- a/arch/arm/mm/dma-mapping.c
> > +++ b/arch/arm/mm/dma-mapping.c
> > @@ -2358,6 +2358,7 @@ static void arm_teardown_iommu_dma_ops(struct device
> *dev)
> > __arm_iommu_detach_device(dev);
> > arm_iommu_release_mapping(mapping);
> > + set_dma_ops(dev, NULL);
> > }
> > #else
>
> The subject mentions arch_teardown_dma_ops(), which I think is correct, but
> the patch adds the set_dma_ops() call to arm_teardown_iommu_dma_ops().
>
> However, the situation is perhaps more complex. Note the check at the
> beginning of arch_setup_dma_ops():
>
> /*
> * Don't override the dma_ops if they have already been set. Ideally
> * this should be the only location where dma_ops are set, remove this
> * check when all other callers of set_dma_ops will have disappeared.
> */
> if (dev->dma_ops)
> return;
>
> If you set the dma_ops to NULL in arm_teardown_iommu_dma_ops() or
> arch_teardown_dma_ops(), the next call to arch_setup_dma_ops() will override
> them. To be safe you should only set them to NULL if they have been set by
> arch_setup_dma_ops(). More than that, arch_teardown_dma_ops() should probably
> not call arm_teardown_iommu_dma_ops() at all if the dma_ops were set by
> arm_iommu_attach_device() and not arch_teardown_dma_ops(). One option would be
> to add a field to struct dev_archdata to store that information. To avoid
> growing the structure, which is embedded in every struct device, you could
> possibly turn the dma_coherent bool into a bitfield.
>
> @@ -19,7 +19,8 @@ struct dev_archdata {
> #ifdef CONFIG_XEN
> const struct dma_map_ops *dev_dma_ops;
> #endif
> - bool dma_coherent;
> + bool dma_coherent:1;
> + bool dma_ops_setup:1;
> };
>
> struct omap_device;
>
> I haven't checked, however, whether the dma_coherent field would need to be
> accessed atomically, so this might be a bad idea.
A bool bit field? :-)
I think I'd just use bool for both. I wouldn't expect dma_coherent change
once it has been set before device driver probe though.
If you like a bit field, then I'd propose making it unsigned int.
--
Regards,
Sakari Ailus
e-mail: sakari.ailus@iki.fi XMPP: sailus@retiisi.org.uk
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next prev parent reply other threads:[~2017-05-16 9:47 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-03 15:48 [PATCH V8 00/11] IOMMU probe deferral support Sricharan R
2017-02-03 15:48 ` [PATCH V8 01/11] iommu/of: Refactor of_iommu_configure() for error handling Sricharan R
2017-03-08 18:58 ` Jean-Philippe Brucker
2017-03-08 19:28 ` Robin Murphy
2017-03-09 9:52 ` sricharan
2017-03-09 11:21 ` Robin Murphy
2017-02-03 15:48 ` [PATCH V8 02/11] iommu/of: Prepare for deferred IOMMU configuration Sricharan R
2017-02-03 15:48 ` [PATCH V8 03/11] of: dma: Move range size workaround to of_dma_get_range() Sricharan R
2017-02-03 15:48 ` [PATCH V8 04/11] of: dma: Make of_dma_deconfigure() public Sricharan R
2017-02-03 15:48 ` [PATCH V8 05/11] ACPI/IORT: Add function to check SMMUs drivers presence Sricharan R
2017-02-03 15:48 ` [PATCH V8 06/11] of/acpi: Configure dma operations at probe time for platform/amba/pci bus devices Sricharan R
2017-02-03 15:48 ` [PATCH V8 07/11] iommu: of: Handle IOMMU lookup failure with deferred probing or error Sricharan R
2017-05-02 18:35 ` Geert Uytterhoeven
2017-05-03 9:54 ` Robin Murphy
2017-05-03 10:24 ` Sricharan R
2017-05-03 11:13 ` Sricharan R
2017-05-05 13:23 ` Geert Uytterhoeven
2017-05-17 9:22 ` Magnus Damm
2017-05-17 10:28 ` Sricharan R
2017-05-15 14:22 ` Will Deacon
2017-05-16 2:26 ` sricharan
2017-05-15 20:37 ` Laurent Pinchart
2017-05-15 21:34 ` Laurent Pinchart
2017-05-16 2:23 ` sricharan
2017-05-16 7:17 ` Laurent Pinchart
2017-05-16 9:47 ` Sakari Ailus [this message]
2017-05-16 13:40 ` sricharan
2017-05-16 14:06 ` Laurent Pinchart
2017-05-16 14:04 ` Robin Murphy
2017-05-16 14:10 ` Laurent Pinchart
2017-05-16 14:29 ` sricharan
2017-05-16 14:46 ` Laurent Pinchart
2017-05-16 14:52 ` Robin Murphy
2017-02-03 15:48 ` [PATCH V8 08/11] drivers: acpi: " Sricharan R
2017-02-03 16:15 ` Sricharan
2017-02-03 17:39 ` Robin Murphy
2017-02-05 6:51 ` Sricharan
2017-02-03 15:48 ` [PATCH V8 09/11] arm64: dma-mapping: Remove the notifier trick to handle early setting of dma_ops Sricharan R
2017-02-03 15:48 ` [PATCH V8 10/11] iommu/arm-smmu: Clean up early-probing workarounds Sricharan R
2017-02-03 15:48 ` [PATCH V8 11/11] ACPI/IORT: Remove linker section for IORT entries probing Sricharan R
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