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

Jonathan Cameron
2019-06-18T15:42:36Z

On Sun, 9 Jun 2019 06:44:02 -0700
Jacob Pan <jacob.jun.pan@linux.intel.com> 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@linux.intel.com>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
> Signed-off-by: Liu, Yi L <yi.l.liu@linux.intel.com>
> Signed-off-by: Ashok Raj <ashok.raj@intel.com>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>

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 */