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

[Jacob Pan]

On Wed, 12 Dec 2018 09:21:43 +0100
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.
> > 
> > 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 am still testing, but just wanted to have feedback on this idea.  
> 
> I am currently respinning this series. Do you have a respin for this
> patch including iommu_register_device_fault_handler with the @id param
> as you suggested above? Otherwise 2 solutions: I keep the code as is
> or I do the modification myself implementing a list of fault_params?
> 
you can keep the code as is if it fits your current needs. Yi and I
have thought of some new cases for supporting mdev. We are thinking to
support many to many handler vs PASID relationship. i.e. allow
registration of many fault handlers per device, each associated with an
ID and data. The use case is that a physical device may register a
fault handler for its own PASID or non-PASID related faults. Such
physical device can also be partitioned into sub-device, e.g. mdev, but
fault handler registration is at physical device level in that IOMMU is
not mdev aware.
Anyway, still need some work to flush out the details.
> Besides do you plans for "[PATCH v5 00/23] IOMMU and VT-d driver
> support for Shared Virtual Address (SVA)" respin - hope I didn't miss
> anything? - ?
> 
You did not miss anything. Yes, we are still working on some internal
integration issues. It should not affect the common interface much. Or
I can send out a common API spin first once we have the functionality
tested.

Thanks for checking.

> Thanks
> 
> Eric
> > 
> > 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]