Re: [PATCH V8 08/11] drivers: acpi: Handle IOMMU lookup failure with deferred probing or error

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On 03/02/17 16:15, Sricharan wrote:
> Hi Lorenzo, Robin,
> 
>> -----Original Message-----
>> From: linux-arm-kernel [mailto:linux-arm-kernel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Sricharan R
>> Sent: Friday, February 03, 2017 9:19 PM
>> To: robin.murphy@xxxxxxx; will.deacon@xxxxxxx; joro@xxxxxxxxxx; lorenzo.pieralisi@xxxxxxx; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx;
>> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-arm-msm@xxxxxxxxxxxxxxx; m.szyprowski@xxxxxxxxxxx; bhelgaas@xxxxxxxxxx; linux-
>> pci@xxxxxxxxxxxxxxx; linux-acpi@xxxxxxxxxxxxxxx; tn@xxxxxxxxxxxx; hanjun.guo@xxxxxxxxxx; okaya@xxxxxxxxxxxxxx
>> Cc: sricharan@xxxxxxxxxxxxxx
>> Subject: [PATCH V8 08/11] drivers: acpi: Handle IOMMU lookup failure with deferred probing or error
>>
>> This is an equivalent to the DT's handling of the iommu master's probe
>> with deferred probing when the corrsponding iommu is not probed yet.
>> 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 firmware 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: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
>> Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
>> Signed-off-by: Sricharan R <sricharan@xxxxxxxxxxxxxx>
>> ---
>> drivers/acpi/arm64/iort.c  | 25 ++++++++++++++++++++++++-
>> drivers/acpi/scan.c        |  7 +++++--
>> drivers/base/dma-mapping.c |  2 +-
>> include/acpi/acpi_bus.h    |  2 +-
>> include/linux/acpi.h       |  7 +++++--
>> 5 files changed, 36 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
>> index bf0ed09..d01bae8 100644
>> --- a/drivers/acpi/arm64/iort.c
>> +++ b/drivers/acpi/arm64/iort.c
>> @@ -550,8 +550,17 @@ static const struct iommu_ops *iort_iommu_xlate(struct device *dev,
>> 			return NULL;
>>
>> 		ops = iommu_get_instance(iort_fwnode);
>> +		/*
>> +		 * If the ops look-up fails, this means that either
>> +		 * the SMMU drivers have not been probed yet or that
>> +		 * the SMMU drivers are not built in the kernel;
>> +		 * Depending on whether the SMMU drivers are built-in
>> +		 * in the kernel or not, defer the IOMMU configuration
>> +		 * or just abort it.
>> +		 */
>> 		if (!ops)
>> -			return NULL;
>> +			return iort_iommu_driver_enabled(node->type) ?
>> +			       ERR_PTR(-EPROBE_DEFER) : NULL;
>>
>> 		ret = arm_smmu_iort_xlate(dev, streamid, iort_fwnode, ops);
>> 	}
>> @@ -625,12 +634,26 @@ const struct iommu_ops *iort_iommu_configure(struct device *dev)
>>
>> 		while (parent) {
>> 			ops = iort_iommu_xlate(dev, parent, streamid);
>> +			if (IS_ERR_OR_NULL(ops))
>> +				return ops;
>>
>> 			parent = iort_node_get_id(node, &streamid,
>> 						  IORT_IOMMU_TYPE, i++);
>> 		}
>> 	}
>>
>> +	/*
>> +	 * If we have reason to believe the IOMMU driver missed the initial
>> +	 * add_device callback for dev, replay it to get things in order.
>> +	 */
>> +	if (!IS_ERR_OR_NULL(ops) && ops->add_device &&
>> +	    dev->bus && !dev->iommu_group) {
>> +		int err = ops->add_device(dev);
>> +
>> +		if (err)
>> +			ops = ERR_PTR(err);
>> +	}
>> +
> 
> On the last post we discussed that the above replay hunk can be made
> common. In trying to do that, i ended up with a patch like below. But not
> sure if that should be a part of this series though. I tested with OF devices
> and would have to be tested with ACPI devices once. Nothing changes
> functionally because of this ideally. Should be split in two patches though.
> 
> Regards,
>  Sricharan
> 
> From aafbf2c97375a086327504f2367eaf9197c719b1 Mon Sep 17 00:00:00 2001
> From: Sricharan R <sricharan@xxxxxxxxxxxxxx>
> Date: Fri, 3 Feb 2017 15:24:47 +0530
> Subject: [PATCH] drivers: iommu: Add iommu_add_device api
> 
> The code to call IOMMU driver's add_device is same
> for both OF and ACPI cases. So add an api which can
> be shared across both the places.
> 
> Also, now with probe-deferral the iommu master devices gets
> added to the respective iommus during probe time instead
> of device creation time. The xlate callbacks of iommu
> drivers are also called only at probe time. As a result
> the add_iommu_group which gets called when the iommu is
> registered to add all devices created before the iommu
> becomes dummy. Similar the BUS_NOTIFY_ADD_DEVICE notification
> also is not needed. So just cleanup those code.
> 
> Signed-off-by: Sricharan R <sricharan@xxxxxxxxxxxxxx>
> ---
>  drivers/acpi/arm64/iort.c | 12 +-------
>  drivers/iommu/iommu.c     | 70 ++++++++++++-----------------------------------
>  drivers/iommu/of_iommu.c  | 11 +-------
>  include/linux/iommu.h     |  8 ++++++
>  4 files changed, 27 insertions(+), 74 deletions(-)
> 
> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> index ac45623..ab2a554 100644
> --- a/drivers/acpi/arm64/iort.c
> +++ b/drivers/acpi/arm64/iort.c
> @@ -642,17 +642,7 @@ const struct iommu_ops *iort_iommu_configure(struct device *dev)
>                 }
>         }
> 
> -       /*
> -        * If we have reason to believe the IOMMU driver missed the initial
> -        * add_device callback for dev, replay it to get things in order.
> -        */
> -       if (!IS_ERR_OR_NULL(ops) && ops->add_device &&
> -           dev->bus && !dev->iommu_group) {
> -               int err = ops->add_device(dev);
> -
> -               if (err)
> -                       ops = ERR_PTR(err);
> -       }
> +       ops = iommu_add_device(dev, ops);
> 
>         return ops;
>  }
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index b752c3d..750552d 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -1015,41 +1015,6 @@ struct iommu_domain *iommu_group_default_domain(struct iommu_group *group)
>         return group->default_domain;
>  }
> 
> -static int add_iommu_group(struct device *dev, void *data)
> -{
> -       struct iommu_callback_data *cb = data;
> -       const struct iommu_ops *ops = cb->ops;
> -       int ret;
> -
> -       if (!ops->add_device)
> -               return 0;
> -
> -       WARN_ON(dev->iommu_group);
> -
> -       ret = ops->add_device(dev);
> -
> -       /*
> -        * We ignore -ENODEV errors for now, as they just mean that the
> -        * device is not translated by an IOMMU. We still care about
> -        * other errors and fail to initialize when they happen.
> -        */
> -       if (ret == -ENODEV)
> -               ret = 0;
> -
> -       return ret;
> -}
> -
> -static int remove_iommu_group(struct device *dev, void *data)
> -{
> -       struct iommu_callback_data *cb = data;
> -       const struct iommu_ops *ops = cb->ops;
> -
> -       if (ops->remove_device && dev->iommu_group)
> -               ops->remove_device(dev);
> -
> -       return 0;
> -}
> -
>  static int iommu_bus_notifier(struct notifier_block *nb,
>                               unsigned long action, void *data)
>  {
> @@ -1059,13 +1024,10 @@ static int iommu_bus_notifier(struct notifier_block *nb,
>         unsigned long group_action = 0;
> 
>         /*
> -        * ADD/DEL call into iommu driver ops if provided, which may
> +        * DEL call into iommu driver ops if provided, which may
>          * result in ADD/DEL notifiers to group->notifier
>          */
> -       if (action == BUS_NOTIFY_ADD_DEVICE) {
> -               if (ops->add_device)
> -                       return ops->add_device(dev);

I'm pretty sure this completely breaks x86 and anyone else...

Anyway, I'd be inclined to leave this alone for now - it's essentially
just a workaround to mesh the per-instance probing behaviour with the
per-bus ops model, so it's bound to be a bit ugly. Moving the IOMMU core
code over to a per-instance model will inevitably subsume the underlying
problem, and I think a bit of duplication is probably the lesser of two
evils in the meantime. On which note, I need to have a good look at
Joerg's shiny new series :)

Robin.

> -       } else if (action == BUS_NOTIFY_REMOVED_DEVICE) {
> +       if (action == BUS_NOTIFY_REMOVED_DEVICE) {
>                 if (ops->remove_device && dev->iommu_group) {
>                         ops->remove_device(dev);
>                         return 0;
> @@ -1107,9 +1069,6 @@ static int iommu_bus_init(struct bus_type *bus, const struct iommu_ops *ops)
>  {
>         int err;
>         struct notifier_block *nb;
> -       struct iommu_callback_data cb = {
> -               .ops = ops,
> -       };
> 
>         nb = kzalloc(sizeof(struct notifier_block), GFP_KERNEL);
>         if (!nb)
> @@ -1121,18 +1080,8 @@ static int iommu_bus_init(struct bus_type *bus, const struct iommu_ops *ops)
>         if (err)
>                 goto out_free;
> 
> -       err = bus_for_each_dev(bus, NULL, &cb, add_iommu_group);
> -       if (err)
> -               goto out_err;
> -
> -
>         return 0;
> 
> -out_err:
> -       /* Clean up */
> -       bus_for_each_dev(bus, NULL, &cb, remove_iommu_group);
> -       bus_unregister_notifier(bus, nb);
> -
>  out_free:
>         kfree(nb);
> 
> @@ -1253,6 +1202,21 @@ static int __iommu_attach_device(struct iommu_domain *domain,
>         return ret;
>  }
> 
> +const struct iommu_ops *iommu_add_device(struct device *dev,
> +                                        const struct iommu_ops *ops)
> +{
> +       if (!IS_ERR_OR_NULL(ops) && ops->add_device &&
> +           dev->bus && !dev->iommu_group) {
> +               int err = ops->add_device(dev);
> +
> +               if (err)
> +                       ops = ERR_PTR(err);
> +       }
> +
> +       return ops;
> +}
> +EXPORT_SYMBOL_GPL(iommu_add_device);
> +
>  int iommu_attach_device(struct iommu_domain *domain, struct device *dev)
>  {
>         struct iommu_group *group;
> diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
> index 2d04663..4b49dc2 100644
> --- a/drivers/iommu/of_iommu.c
> +++ b/drivers/iommu/of_iommu.c
> @@ -224,17 +224,8 @@ const struct iommu_ops *of_iommu_configure(struct device *dev,
>                 ops = of_pci_iommu_init(to_pci_dev(dev), master_np);
>         else
>                 ops = of_platform_iommu_init(dev, master_np);
> -       /*
> -        * If we have reason to believe the IOMMU driver missed the initial
> -        * add_device callback for dev, replay it to get things in order.
> -        */
> -       if (!IS_ERR_OR_NULL(ops) && ops->add_device &&
> -           dev->bus && !dev->iommu_group) {
> -               int err = ops->add_device(dev);
> 
> -               if (err)
> -                       ops = ERR_PTR(err);
> -       }
> +       ops = iommu_add_device(dev, ops);
> 
>         return ops;
>  }
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index add30c3..1d54a91 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -232,6 +232,8 @@ struct iommu_ops {
>  extern struct iommu_domain *iommu_domain_alloc(struct bus_type *bus);
>  extern struct iommu_group *iommu_group_get_by_id(int id);
>  extern void iommu_domain_free(struct iommu_domain *domain);
> +extern const struct iommu_ops *iommu_add_device(struct device *dev,
> +                                               const struct iommu_ops *ops);
>  extern int iommu_attach_device(struct iommu_domain *domain,
>                                struct device *dev);
>  extern void iommu_detach_device(struct iommu_domain *domain,
> @@ -405,6 +407,12 @@ static inline void iommu_domain_free(struct iommu_domain *domain)
>  {
>  }
> 
> +static inline const struct iommu_ops *iommu_add_device(struct device *dev,
> +                                             const struct iommu_ops *ops)
> +{
> +       return NULL;
> +}
> +
>  static inline int iommu_attach_device(struct iommu_domain *domain,
>                                       struct device *dev)
>  {
> --
> 1.8.2.1
> 

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