Re: [RFC v3 14/21] iommu: introduce device fault data

Jacob Pan
2019-01-14T22:32:08Z

On Fri, 11 Jan 2019 11:06:29 +0000
Jean-Philippe Brucker <jean-philippe.brucker@arm.com> wrote:

> On 10/01/2019 18:45, Jacob Pan wrote:
> > On Tue, 8 Jan 2019 11:26:26 +0100
> > Eric Auger <eric.auger@redhat.com> wrote:
> >
> >> From: Jacob Pan <jacob.jun.pan@linux.intel.com>
> >>
> >> 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@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> [moved part of the iommu_fault_event
> >> struct in the uapi, enriched the fault reasons to be able to map
> >> unrecoverable SMMUv3 errors] ---
> >> 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 244c1a3d5989..1dedc2d247c2 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 */ @@ -255,6 +259,52 @@ 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;
> > I think we want to move device_private to uapi since it gets
> > injected into the guest, then returned by guest in case of page
> > response. For VT-d we also need 128 bits of private data. VT-d
> > spec. 7.7.1
>
> Ah, I didn't notice the format changed in VT-d rev3. On that topic,
> how do we manage future extensions to the iommu_fault struct? Should
> we add ~48 bytes of padding after device_private, along with some
> flags telling which field is valid, or deal with it using a structure
> version like we do for the invalidate and bind structs? In the first
> case, iommu_fault wouldn't fit in a 64-byte cacheline anymore, but
> I'm not sure we care.
>
IMHO, I like version and padding. I don't see a need for flags once we
have version.

> > For exception tracking (e.g. unanswered page request), I can add
> > timer and list info later when I include PRQ. sounds ok?
> >> + u64 iommu_private;
> [...]
> >> +/**
> >> + * 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;
>
> What does @access contain? Can it be squashed into @prot?
>
I agreed.

how about this?
#define IOMMU_FAULT_VERSION_V1 0x1
struct iommu_fault {
__u16 version;
__u16 type;
__u32 reason;
__u64 addr;
__u32 pasid;
__u32 page_req_group_id;
__u32 last_req : 1;
__u32 pasid_valid : 1;
__u32 prot;
__u64 device_private[2];
__u8 padding[48];
};

> Thanks,
> Jean
>
> > relocated to uapi, Yi can you confirm?
> > __u64 device_private[2];
> >
> >> +};
> >> #endif /* _UAPI_IOMMU_H */
> >
> > _______________________________________________
> > iommu mailing list
> > iommu@lists.linux-foundation.org
> > https://lists.linuxfoundation.org/mailman/listinfo/iommu
> >
>

[Jacob Pan]