linux-kernel - RE: [PATCH v4 10/22] iommu: introduce device fault data

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Date:   Sun, 20 May 2018 08:17:43 +0000
From:   "Liu, Yi L" <yi.l.liu@...el.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
CC:     "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        Jean Delvare <khali@...ux-fr.org>,
        Christoph Hellwig <hch@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Yi L <yi.l.liu@...ux.intel.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        "David Woodhouse" <dwmw2@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Jean-Philippe Brucker <jean-philippe.brucker@....com>
Subject: RE: [PATCH v4 10/22] iommu: introduce device fault data

Hi Jacob,

> From: Jacob Pan [mailto:jacob.jun.pan@...ux.intel.com]
> Sent: Tuesday, April 17, 2018 5:49 AM
>  include/linux/iommu.h | 102
> +++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 100 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index e963dbd..8968933 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    */
> @@ -264,6 +268,99 @@ struct iommu_device {
>  	struct device *dev;
>  };
> 
> +/*  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 */
> +	IOMMU_FAULT_REASON_PASID_FETCH,
> +
> +	/*
> +	 * PASID is out of range (e.g. exceeds the maximum PASID
> +	 * supported by the IOMMU) or disabled.
> +	 */
> +	IOMMU_FAULT_REASON_PASID_INVALID,
> +
> +	/* Could not access the page directory (Invalid PASID entry) */
> +	IOMMU_FAULT_REASON_PGD_FETCH,
> +
> +	/* Could not access the page table entry (Bad address) */
> +	IOMMU_FAULT_REASON_PTE_FETCH,
> +
> +	/* Protection flag check failed */
> +	IOMMU_FAULT_REASON_PERMISSION,
> +};
> +
> +/**
> + * 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
> +
> + * @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
> + * @pasid: contains process address space ID, used in shared virtual memory(SVM)
> + * @rid: requestor ID
> + * @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, e.g. IOMMU_FAULT_READ,
> IOMMU_FAULT_WRITE
> + * @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 {
> +	enum iommu_fault_type type;
> +	enum iommu_fault_reason reason;
> +	u64 addr;
> +	u32 pasid;
> +	u32 page_req_group_id;
> +	u32 last_req : 1;
> +	u32 pasid_valid : 1;
> +	u32 prot;

I think userspace also needs to know the fault type, reason, pasid, addr, goup_id,
prot. So the definition should be included in uapi/Linux/iommu.h.

This comment also applies to "struct page_response_msg". Qemu also wants to
pass the page response to host.

> +	u64 device_private;
> +	u64 iommu_private;

These two seems to be in kernel driver specific data. May split the iommu_fault_event
definition into two parts. One part for the data required by both driver and userspace.
One part for in kernel driver specific data.

Thanks,
Yi Liu