Re: [RFC v2 14/20] iommu: introduce device fault data

[Auger Eric]

Hi Jacob,

On 9/21/18 12:06 AM, Jacob Pan wrote:
> On Tue, 18 Sep 2018 16:24:51 +0200
> Eric Auger <eric.auger@xxxxxxxxxx> wrote:
> 
>> From: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
>>
>> Device faults detected by IOMMU can be reported outside IOMMU
>> subsystem for further processing. This patch intends to provide
>> a generic device fault data such that device drivers can be
>> communicated with IOMMU faults without model specific knowledge.
>>
>> The proposed format is the result of discussion at:
>> https://lkml.org/lkml/2017/11/10/291
>> Part of the code is based on Jean-Philippe Brucker's patchset
>> (https://patchwork.kernel.org/patch/9989315/).
>>
>> The assumption is that model specific IOMMU driver can filter and
>> handle most of the internal faults if the cause is within IOMMU driver
>> control. Therefore, the fault reasons can be reported are grouped
>> and generalized based common specifications such as PCI ATS.
>>
>> Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
>> Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx>
>> Signed-off-by: Liu, Yi L <yi.l.liu@xxxxxxxxxxxxxxx>
>> Signed-off-by: Ashok Raj <ashok.raj@xxxxxxxxx>
>> Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx>
>> [moved part of the iommu_fault_event struct in the uapi, enriched
>>  the fault reasons to be able to map unrecoverable SMMUv3 errors]
> Sounds good to me.
> There are also other "enrichment" we need to do to support mdev or
> finer granularity fault reporting below physical device. e.g. PASID
> level.

Actually I intended to send you an email about those iommu_fault_reason
enum value changes. To attach this discussion to your original series, I
will send a separate email in the "[PATCH v5 00/23] IOMMU and VT-d
driver support for Shared Virtual Address (SVA)" thread.
> 
> The current scheme works for PCIe physical device level, where each
> device registers a single handler only once. When device fault is
> detected by the IOMMU, it will find the matching handler and private
> data to report back. However, for devices partitioned by PASID and
> represented by mdev this may not work. Since IOMMU is not mdev aware
> and only works at physical device level.
> So I am thinking we should allow multiple registration of fault handler
> with different data and ID. i.e.
> 
> int iommu_register_device_fault_handler(struct device *dev,
> 					iommu_dev_fault_handler_t handler,
> 					int id,
> 					void *data)
> 
> where the new "id field" is
>  * @id: Identification of the handler private data, will be used by fault
>  *      reporting code to match the handler data to be returned. For page
>  *      request, this can be the PASID. ID must be unique per device, i.e.
>  *      each ID can only be registered once per device.
>  *      - IOMMU_DEV_FAULT_ID_UNRECOVERY (~0U) is reserved for fault reporting
>  *      w/o ID. e.g. unrecoverable faults.
I don't get this last sentence. Don't you need the feature also for
unrecoverable faults, ie. isn't it requested to report an unrecoverable
fault on a specific id?

Otherwise looks OK; but I still need to carefully review "[RFC PATCH v2
00/10] vfio/mdev: IOMMU aware mediated device".

Thanks

Eric
> 
> I am still testing, but just wanted to have feedback on this idea.
> 
> Thanks,
> 
> Jacob
> 
> 
>> ---
>>  include/linux/iommu.h      | 55 ++++++++++++++++++++++++-
>>  include/uapi/linux/iommu.h | 83
>> ++++++++++++++++++++++++++++++++++++++ 2 files changed, 136
>> insertions(+), 2 deletions(-)
>>
>> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
>> index 9bd3e63d562b..7529c14ff506 100644
>> --- a/include/linux/iommu.h
>> +++ b/include/linux/iommu.h
>> @@ -49,13 +49,17 @@ struct bus_type;
>>  struct device;
>>  struct iommu_domain;
>>  struct notifier_block;
>> +struct iommu_fault_event;
>>  
>>  /* iommu fault flags */
>> -#define IOMMU_FAULT_READ	0x0
>> -#define IOMMU_FAULT_WRITE	0x1
>> +#define IOMMU_FAULT_READ		(1 << 0)
>> +#define IOMMU_FAULT_WRITE		(1 << 1)
>> +#define IOMMU_FAULT_EXEC		(1 << 2)
>> +#define IOMMU_FAULT_PRIV		(1 << 3)
>>  
>>  typedef int (*iommu_fault_handler_t)(struct iommu_domain *,
>>  			struct device *, unsigned long, int, void *);
>> +typedef int (*iommu_dev_fault_handler_t)(struct iommu_fault_event *,
>> void *); 
>>  struct iommu_domain_geometry {
>>  	dma_addr_t aperture_start; /* First address that can be
>> mapped    */ @@ -262,6 +266,52 @@ struct iommu_device {
>>  	struct device *dev;
>>  };
>>  
>> +/**
>> + * struct iommu_fault_event - Generic per device fault data
>> + *
>> + * - PCI and non-PCI devices
>> + * - Recoverable faults (e.g. page request), information based on
>> PCI ATS
>> + * and PASID spec.
>> + * - Un-recoverable faults of device interest
>> + * - DMA remapping and IRQ remapping faults
>> + *
>> + * @fault: fault descriptor
>> + * @device_private: if present, uniquely identify device-specific
>> + *                  private data for an individual page request.
>> + * @iommu_private: used by the IOMMU driver for storing
>> fault-specific
>> + *                 data. Users should not modify this field before
>> + *                 sending the fault response.
>> + */
>> +struct iommu_fault_event {
>> +	struct iommu_fault fault;
>> +	u64 device_private;
>> +	u64 iommu_private;
>> +};
>> +
>> +/**
>> + * struct iommu_fault_param - per-device IOMMU fault data
>> + * @dev_fault_handler: Callback function to handle IOMMU faults at
>> device level
>> + * @data: handler private data
>> + *
>> + */
>> +struct iommu_fault_param {
>> +	iommu_dev_fault_handler_t handler;
>> +	void *data;
>> +};
>> +
>> +/**
>> + * struct iommu_param - collection of per-device IOMMU data
>> + *
>> + * @fault_param: IOMMU detected device fault reporting data
>> + *
>> + * TODO: migrate other per device data pointers under
>> iommu_dev_data, e.g.
>> + *	struct iommu_group	*iommu_group;
>> + *	struct iommu_fwspec	*iommu_fwspec;
>> + */
>> +struct iommu_param {
>> +	struct iommu_fault_param *fault_param;
>> +};
>> +
>>  int  iommu_device_register(struct iommu_device *iommu);
>>  void iommu_device_unregister(struct iommu_device *iommu);
>>  int  iommu_device_sysfs_add(struct iommu_device *iommu,
>> @@ -429,6 +479,7 @@ struct iommu_ops {};
>>  struct iommu_group {};
>>  struct iommu_fwspec {};
>>  struct iommu_device {};
>> +struct iommu_fault_param {};
>>  
>>  static inline bool iommu_present(struct bus_type *bus)
>>  {
>> diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h
>> index 21adb2a964e5..a0fe5c2fb236 100644
>> --- a/include/uapi/linux/iommu.h
>> +++ b/include/uapi/linux/iommu.h
>> @@ -150,5 +150,88 @@ struct iommu_guest_msi_binding {
>>  	__u64		gpa;
>>  	__u32		granule;
>>  };
>> +
>> +/*  Generic fault types, can be expanded IRQ remapping fault */
>> +enum iommu_fault_type {
>> +	IOMMU_FAULT_DMA_UNRECOV = 1,	/* unrecoverable fault */
>> +	IOMMU_FAULT_PAGE_REQ,		/* page request fault */
>> +};
>> +
>> +enum iommu_fault_reason {
>> +	IOMMU_FAULT_REASON_UNKNOWN = 0,
>> +
>> +	/* IOMMU internal error, no specific reason to report out */
>> +	IOMMU_FAULT_REASON_INTERNAL,
>> +
>> +	/* Could not access the PASID table (fetch caused external
>> abort) */
>> +	IOMMU_FAULT_REASON_PASID_FETCH,
>> +
>> +	/* could not access the device context (fetch caused
>> external abort) */
>> +	IOMMU_FAULT_REASON_DEVICE_CONTEXT_FETCH,
>> +
>> +	/* pasid entry is invalid or has configuration errors */
>> +	IOMMU_FAULT_REASON_BAD_PASID_ENTRY,
>> +
>> +	/* device context entry is invalid or has configuration
>> errors */
>> +	IOMMU_FAULT_REASON_BAD_DEVICE_CONTEXT_ENTRY,
>> +	/*
>> +	 * PASID is out of range (e.g. exceeds the maximum PASID
>> +	 * supported by the IOMMU) or disabled.
>> +	 */
>> +	IOMMU_FAULT_REASON_PASID_INVALID,
>> +
>> +	/* source id is out of range */
>> +	IOMMU_FAULT_REASON_SOURCEID_INVALID,
>> +
>> +	/*
>> +	 * An external abort occurred fetching (or updating) a
>> translation
>> +	 * table descriptor
>> +	 */
>> +	IOMMU_FAULT_REASON_WALK_EABT,
>> +
>> +	/*
>> +	 * Could not access the page table entry (Bad address),
>> +	 * actual translation fault
>> +	 */
>> +	IOMMU_FAULT_REASON_PTE_FETCH,
>> +
>> +	/* Protection flag check failed */
>> +	IOMMU_FAULT_REASON_PERMISSION,
>> +
>> +	/* access flag check failed */
>> +	IOMMU_FAULT_REASON_ACCESS,
>> +
>> +	/* Output address of a translation stage caused Address Size
>> fault */
>> +	IOMMU_FAULT_REASON_OOR_ADDRESS
>> +};
>> +
>> +/**
>> + * struct iommu_fault - Generic fault data
>> + *
>> + * @type contains fault type
>> + * @reason fault reasons if relevant outside IOMMU driver.
>> + * IOMMU driver internal faults are not reported.
>> + * @addr: tells the offending page address
>> + * @fetch_addr: tells the address that caused an abort, if any
>> + * @pasid: contains process address space ID, used in shared virtual
>> memory
>> + * @page_req_group_id: page request group index
>> + * @last_req: last request in a page request group
>> + * @pasid_valid: indicates if the PRQ has a valid PASID
>> + * @prot: page access protection flag:
>> + *	IOMMU_FAULT_READ, IOMMU_FAULT_WRITE
>> + */
>> +
>> +struct iommu_fault {
>> +	__u32	type;   /* enum iommu_fault_type */
>> +	__u32	reason; /* enum iommu_fault_reason */
>> +	__u64	addr;
>> +	__u64	fetch_addr;
>> +	__u32	pasid;
>> +	__u32	page_req_group_id;
>> +	__u32	last_req;
>> +	__u32	pasid_valid;
>> +	__u32	prot;
>> +	__u32	access;
>> +};
>>  #endif /* _UAPI_IOMMU_H */
>>  
> 
> [Jacob Pan]
>