Re: [PATCH v4 02/22] iommu: Introduce device fault data

[Jonathan Cameron]

On Sun, 9 Jun 2019 06:44:02 -0700
Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx> wrote:

> Device faults detected by IOMMU can be reported outside the IOMMU
> subsystem for further processing. This patch introduces
> a generic device fault data structure.
> 
> The fault can be either an unrecoverable fault or a page request,
> also referred to as a recoverable fault.
> 
> We only care about non internal faults that are likely to be reported
> to an external subsystem.
> 
> 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>

A few trivial nitpicks in here.

Otherwise looks straight forward and sensible to me.

Jonathan
> ---
>  include/linux/iommu.h      |  44 +++++++++++++++++
>  include/uapi/linux/iommu.h | 118 +++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 162 insertions(+)
>  create mode 100644 include/uapi/linux/iommu.h
> 
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index a815cf6..7890a92 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -25,6 +25,7 @@
>  #include <linux/errno.h>
>  #include <linux/err.h>
>  #include <linux/of.h>
> +#include <uapi/linux/iommu.h>
>  
>  #define IOMMU_READ	(1 << 0)
>  #define IOMMU_WRITE	(1 << 1)
> @@ -49,6 +50,7 @@ struct device;
>  struct iommu_domain;
>  struct notifier_block;
>  struct iommu_sva;
> +struct iommu_fault_event;
>  
>  /* iommu fault flags */
>  #define IOMMU_FAULT_READ	0x0
> @@ -58,6 +60,7 @@ typedef int (*iommu_fault_handler_t)(struct iommu_domain *,
>  			struct device *, unsigned long, int, void *);
>  typedef int (*iommu_mm_exit_handler_t)(struct device *dev, struct iommu_sva *,
>  				       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    */
> @@ -301,6 +304,46 @@ struct iommu_device {
>  	struct device *dev;
>  };
>  
> +/**
> + * struct iommu_fault_event - Generic fault event
> + *
> + * Can represent recoverable faults such as a page requests or
> + * unrecoverable faults such as DMA or IRQ remapping faults.
> + *
> + * @fault: fault descriptor
> + * @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 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
> + *

No need for this blank line.  Seems inconsistent with other docs in here.

Also, there is a docs fixup in patch 3 which should be pulled back to here.

> + */
> +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;
Is it actually worth having the indirection of a pointer here as opposed
to just embedding the actual structure?  The null value is used in places
but can just use the handler being null for the same job I think...

It reduces the code needed in patch 3 a bit.

It gets a bit bigger in patch 4, but is still only about 16 bytes.

> +};
> +
>  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,
> @@ -504,6 +547,7 @@ 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
> new file mode 100644
> index 0000000..aaa3b6a
> --- /dev/null
> +++ b/include/uapi/linux/iommu.h
> @@ -0,0 +1,118 @@
> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> +/*
> + * IOMMU user API definitions
> + */
> +
> +#ifndef _UAPI_IOMMU_H
> +#define _UAPI_IOMMU_H
> +
> +#include <linux/types.h>
> +
> +#define IOMMU_FAULT_PERM_READ	(1 << 0) /* read */
> +#define IOMMU_FAULT_PERM_WRITE	(1 << 1) /* write */
> +#define IOMMU_FAULT_PERM_EXEC	(1 << 2) /* exec */
> +#define IOMMU_FAULT_PERM_PRIV	(1 << 3) /* privileged */
> +
> +/* 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,
> +
> +	/* Could not access the PASID table (fetch caused external abort) */
> +	IOMMU_FAULT_REASON_PASID_FETCH,
> +
> +	/* PASID entry is invalid or has configuration errors */
> +	IOMMU_FAULT_REASON_BAD_PASID_ENTRY,
> +
> +	/*
> +	 * PASID is out of range (e.g. exceeds the maximum PASID
> +	 * supported by the IOMMU) or disabled.
> +	 */
> +	IOMMU_FAULT_REASON_PASID_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 */

Nitpick: Inconsistent capitalization of first word in comment :)

> +	IOMMU_FAULT_REASON_ACCESS,
> +
> +	/* Output address of a translation stage caused Address Size fault */
> +	IOMMU_FAULT_REASON_OOR_ADDRESS,
> +};
> +
> +/**
> + * struct iommu_fault_unrecoverable - Unrecoverable fault data
> + * @reason: reason of the fault, from &enum iommu_fault_reason
> + * @flags: parameters of this fault (IOMMU_FAULT_UNRECOV_* values)
> + * @pasid: Process Address Space ID
> + * @perm: Requested permission access using by the incoming transaction
> + *        (IOMMU_FAULT_PERM_* values)
> + * @addr: offending page address
> + * @fetch_addr: address that caused a fetch abort, if any
> + */
> +struct iommu_fault_unrecoverable {
> +	__u32	reason;
> +#define IOMMU_FAULT_UNRECOV_PASID_VALID		(1 << 0)
> +#define IOMMU_FAULT_UNRECOV_ADDR_VALID		(1 << 1)
> +#define IOMMU_FAULT_UNRECOV_FETCH_ADDR_VALID	(1 << 2)
> +	__u32	flags;
> +	__u32	pasid;
> +	__u32	perm;
> +	__u64	addr;
> +	__u64	fetch_addr;
> +};
> +
> +/**
> + * struct iommu_fault_page_request - Page Request data
> + * @flags: encodes whether the corresponding fields are valid and whether this
> + *         is the last page in group (IOMMU_FAULT_PAGE_REQUEST_* values)
> + * @pasid: Process Address Space ID
> + * @grpid: Page Request Group Index
> + * @perm: requested page permissions (IOMMU_FAULT_PERM_* values)
> + * @addr: page address
> + * @private_data: device-specific private information
> + */

Slightly surprised to see this given cover letter says no PRS.
I guess it is part of the original patch rather than intended
for this series.. Not a problem as far as I'm concerned.

> +struct iommu_fault_page_request {
> +#define IOMMU_FAULT_PAGE_REQUEST_PASID_VALID	(1 << 0)
> +#define IOMMU_FAULT_PAGE_REQUEST_LAST_PAGE	(1 << 1)
> +#define IOMMU_FAULT_PAGE_REQUEST_PRIV_DATA	(1 << 2)
> +	__u32	flags;
> +	__u32	pasid;
> +	__u32	grpid;
> +	__u32	perm;
> +	__u64	addr;
> +	__u64	private_data[2];
> +};
> +
> +/**
> + * struct iommu_fault - Generic fault data
> + * @type: fault type from &enum iommu_fault_type
> + * @padding: reserved for future use (should be zero)
> + * @event: Fault event, when @type is %IOMMU_FAULT_DMA_UNRECOV
> + * @prm: Page Request message, when @type is %IOMMU_FAULT_PAGE_REQ
> + */
> +struct iommu_fault {
> +	__u32	type;
> +	__u32	padding;
> +	union {
> +		struct iommu_fault_unrecoverable event;
> +		struct iommu_fault_page_request prm;
> +	};
> +};
> +#endif /* _UAPI_IOMMU_H */