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

[Jacob Pan]

On Fri, 21 Sep 2018 11:54:56 +0200
Auger Eric <eric.auger@xxxxxxxxxx> wrote:

> 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?
> 
For unrecoverable faults which are not associated with a specific PASID,
we reserve a range of special IDs for them. Let me rewrite the
comments.
The usage would be:
For Handler registration by vfio or device driver
1.  PRQ of PASID1
iommu_register_device_fault_handler(pdev, handler, pasid1, data1);
2.  PRQ of PASID2
iommu_register_device_fault_handler(pdev, handler, pasid2, data2);
3. unrecoverable fault
iommu_register_device_fault_handler(pdev, handler,
IOMMU_DEV_FAULT_ID_UNRECOVERY, NULL);

For IOMMU driver reporting fault back to vfio or kernel driver:
1. PRQ of PASID1
iommu_report_device_fault(dev, evt1)
where evt1->data = data1, evt1->pasid = pasid1
2. PRQ of PASID2
iommu_report_device_fault(dev, evt2)
where evt2->data = data2, evt2->pasid = pasid2
3. unrecoverable fault
iommu_report_device_fault(dev, evt)
where evt2->data = NULL, evt->pasid = IOMMU_DEV_FAULT_ID_UNRECOVERY

where evt is of struct iommu_fault_event.

> 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]
> >   

[Jacob Pan]