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Date:   Fri, 24 May 2019 06:49:24 -0700
From:   Jacob Pan <jacob.jun.pan@linux.intel.com>
To:     Robin Murphy <robin.murphy@arm.com>
Cc:     Jean-Philippe Brucker <jean-philippe.brucker@arm.com>,
        joro@8bytes.org, alex.williamson@redhat.com,
        yi.l.liu@linux.intel.com, iommu@lists.linux-foundation.org,
        ashok.raj@intel.com, linux-kernel@vger.kernel.org,
        jacob.jun.pan@linux.intel.com
Subject: Re: [PATCH 2/4] iommu: Introduce device fault data
Message-ID: <20190524064924.0cc92ae3@jacob-builder>
In-Reply-To: <791fe9b1-5d85-fd2d-7cfb-c2fb3428deb6@arm.com>
References: <20190523180613.55049-1-jean-philippe.brucker@arm.com>
        <20190523180613.55049-3-jean-philippe.brucker@arm.com>
        <791fe9b1-5d85-fd2d-7cfb-c2fb3428deb6@arm.com>
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On Thu, 23 May 2019 19:43:46 +0100
Robin Murphy <robin.murphy@arm.com> wrote:

> On 23/05/2019 19:06, Jean-Philippe Brucker wrote:
> > From: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > 
> > 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>
> > ---
> >   include/linux/iommu.h      |  43 ++++++++++++++
> >   include/uapi/linux/iommu.h | 118
> > +++++++++++++++++++++++++++++++++++++ 2 files changed, 161
> > insertions(+) create mode 100644 include/uapi/linux/iommu.h
> > 
> > diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> > index a815cf6f6f47..d442f5f3fa93 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 +304,45 @@ 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.  
> 
> Sorry if I'm a bit late to the party, but given that description, if 
> users aren't allowed to touch this then why expose it to them at all? 
> I.e. why not have iommu_report_device_fault() pass just the fault
> itself to the fault handler:
> 
> 	ret = fparam->handler(&evt->fault, fparam->data);
> 
> and let the IOMMU core/drivers decapsulate it again later if need be. 
> AFAICS drivers could also just embed the entire generic event in
> their own private structure anyway, just as we do for domains.
> 
I can't remember all the discussion history but I think iommu_private
is used similarly to the page request private data (device private). We
need to inject the data to the guest and the guest will send the
unmodified data back along with response. The private data can be used
to tag internal device/iommu context.

I think we can do the way you said by keeping them within iommu core
and recover it based on the response but that would require tracking
each fault report, right?

If we pass on the private data, we only need to check if the response
belong to the device but not exact match of a specific fault since the
damage is contained in the assigned device. In case of injection
fault into the guest, the response will come asynchronously after the
handler completes.

> Robin.
> 
> > + */
> > +struct iommu_fault_event {
> > +	struct iommu_fault fault;
> > +	u64 iommu_private;
> > +};
> > +
> > +/**
> > + * struct iommu_fault_param - per-device IOMMU fault data
> > + * @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,
> > @@ -504,6 +546,7 @@ 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 000000000000..796402174d6c
> > --- /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 */
> > +	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
> > + */
> > +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 */
> >   
> _______________________________________________
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> iommu@lists.linux-foundation.org
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[Jacob Pan]