Re: [PATCH v4 0/8] vfio/mdev: IOMMU aware mediated device

[Xu Zaibo <xuzaibo@huawei.com>]

Hi,
>>
>> Is this solution trying to support general user space processes who 
>> are directly working on devices?
>
> Yes, it is.
>

Okay. But I got another question. As I write a Crypto driver, could I 
call 'mdev_register_device'?
Or in other words, is 'mdev_register_device' acceptable for drivers of 
Crypto?

+cc: Herbert Xu

Thanks,
Zaibo

>>
>>
>> On 2018/11/5 15:34, Lu Baolu wrote:
>>> Hi,
>>>
>>> The Mediate Device is a framework for fine-grained physical device
>>> sharing across the isolated domains. Currently the mdev framework
>>> is designed to be independent of the platform IOMMU support. As the
>>> result, the DMA isolation relies on the mdev parent device in a
>>> vendor specific way.
>>>
>>> There are several cases where a mediated device could be protected
>>> and isolated by the platform IOMMU. For example, Intel vt-d rev3.0
>>> [1] introduces a new translation mode called 'scalable mode', which
>>> enables PASID-granular translations. The vt-d scalable mode is the
>>> key ingredient for Scalable I/O Virtualization [2] [3] which allows
>>> sharing a device in minimal possible granularity (ADI - Assignable
>>> Device Interface).
>>>
>>> A mediated device backed by an ADI could be protected and isolated
>>> by the IOMMU since 1) the parent device supports tagging an unique
>>> PASID to all DMA traffic out of the mediated device; and 2) the DMA
>>> translation unit (IOMMU) supports the PASID granular translation.
>>> We can apply IOMMU protection and isolation to this kind of devices
>>> just as what we are doing with an assignable PCI device.
>>>
>>> In order to distinguish the IOMMU-capable mediated devices from those
>>> which still need to rely on parent devices, this patch set adds two
>>> new members in struct mdev_device.
>>>
>>> * iommu_device
>>>    - This, if set, indicates that the mediated device could
>>>      be fully isolated and protected by IOMMU via attaching
>>>      an iommu domain to this device. If empty, it indicates
>>>      using vendor defined isolation.
>>>
>>> * iommu_domain
>>>    - This is a place holder for an iommu domain. A domain
>>>      could be store here for later use once it has been
>>>      attached to the iommu_device of this mdev.
>>>
>>> Below helpers are added to set and get above iommu device
>>> and iommu domain pointers in mdev core implementation.
>>>
>>> * mdev_set/get_iommu_device(dev, iommu_device)
>>>    - Set or get the iommu device which represents this mdev
>>>      in IOMMU's device scope. Drivers don't need to set the
>>>      iommu device if it uses vendor defined isolation.
>>>
>>> * mdev_set/get_iommu_domain(domain)
>>>    - A iommu domain which has been attached to the iommu
>>>      device in order to protect and isolate the mediated
>>>      device will be kept in the mdev data structure and
>>>      could be retrieved later.
>>>
>>> The mdev parent device driver could opt-in that the mdev could be
>>> fully isolated and protected by the IOMMU when the mdev is being
>>> created by invoking mdev_set_iommu_device() in its @create().
>>>
>>> In the vfio_iommu_type1_attach_group(), a domain allocated through
>>> iommu_domain_alloc() will be attached to the mdev iommu device if
>>> an iommu device has been set. Otherwise, the dummy external domain
>>> will be used and all the DMA isolation and protection are routed to
>>> parent driver as the result.
>>>
>>> On IOMMU side, a basic requirement is allowing to attach multiple
>>> domains to a PCI device if the device advertises the capability
>>> and the IOMMU hardware supports finer granularity translations than
>>> the normal PCI Source ID based translation.
>>>
>>> As the result, a PCI device could work in two modes: normal mode
>>> and auxiliary mode. In the normal mode, a pci device could be
>>> isolated in the Source ID granularity; the pci device itself could
>>> be assigned to a user application by attaching a single domain
>>> to it. In the auxiliary mode, a pci device could be isolated in
>>> finer granularity, hence subsets of the device could be assigned
>>> to different user level application by attaching a different domain
>>> to each subset.
>>>
>>> The device driver is able to switch between above two modes with
>>> below interfaces:
>>>
>>> * iommu_get_dev_attr(dev, IOMMU_DEV_ATTR_AUXD_CAPABILITY)
>>>    - Represents the ability of supporting multiple domains
>>>      per device.
>>>
>>> * iommu_set_dev_attr(dev, IOMMU_DEV_ATTR_AUXD_ENABLE)
>>>    - Enable the multiple domains capability for the device
>>>      referenced by @dev.
>>>
>>> * iommu_set_dev_attr(dev, IOMMU_DEV_ATTR_AUXD_DISABLE)
>>>    - Disable the multiple domains capability for the device
>>>      referenced by @dev.
>>>
>>> * iommu_domain_get_attr(domain, DOMAIN_ATTR_AUXD_ID)
>>>    - Return ID used for finer-granularity DMA translation.
>>>
>>> * iommu_attach_device_aux(domain, dev)
>>>    - Attach a domain to the device in the auxiliary mode.
>>>
>>> * iommu_detach_device_aux(domain, dev)
>>>    - Detach the aux domain from device.
>>>
>>> In order for the ease of discussion, sometimes we call "a domain in
>>> auxiliary mode' or simply 'an auxiliary domain' when a domain is
>>> attached to a device for finer granularity translations. But we need
>>> to keep in mind that this doesn't mean there is a differnt domain
>>> type. A same domain could be bound to a device for Source ID based
>>> translation, and bound to another device for finer granularity
>>> translation at the same time.
>>>
>>> This patch series extends both IOMMU and vfio components to support
>>> mdev device passing through when it could be isolated and protected
>>> by the IOMMU units. The first part of this series (PATCH 1/08~5/08)
>>> adds the interfaces and implementation of the multiple domains per
>>> device. The second part (PATCH 6/08~8/08) adds the iommu device
>>> attribute to each mdev, determines isolation type according to the
>>> existence of an iommu device when attaching group in vfio type1 iommu
>>> module, and attaches the domain to iommu aware mediated devices.
>>>
>>> This patch series depends on a patch set posted here [4] for discussion
>>> which added scalable mode support in Intel IOMMU driver.
>>>
>>> References:
>>> [1] 
>>> https://software.intel.com/en-us/download/intel-virtualization-technology-for-directed-io-architecture-specification 
>>>
>>> [2] 
>>> https://software.intel.com/en-us/download/intel-scalable-io-virtualization-technical-specification 
>>>
>>> [3] https://schd.ws/hosted_files/lc32018/00/LC3-SIOV-final.pdf
>>> [4] https://lkml.org/lkml/2018/11/5/136
>>>
>>> Best regards,
>>> Lu Baolu
>>>
>>> Change log:
>>>    v3->v4:
>>>    - Use aux domain specific interfaces for domain attach and detach.
>>>    - Rebase all patches to 4.20-rc1.
>>>
>>>    v2->v3:
>>>    - Remove domain type enum and use a pointer on mdev_device instead.
>>>    - Add a generic interface for getting/setting per device iommu
>>>      attributions. And use it for query aux domain capability, enable
>>>      aux domain and disable aux domain purpose.
>>>    - Reuse iommu_domain_get_attr() to retrieve the id in a aux domain.
>>>    - We discussed the impact of the default domain implementation
>>>      on reusing iommu_at(de)tach_device() interfaces. We agreed
>>>      that reusing iommu_at(de)tach_device() interfaces is the right
>>>      direction and we could tweak the code to remove the impact.
>>>      https://www.spinics.net/lists/kvm/msg175285.html
>>>    - Removed the RFC tag since no objections received.
>>>    - This patch has been submitted separately.
>>>      https://www.spinics.net/lists/kvm/msg173936.html
>>>
>>>    v1->v2:
>>>    - Rewrite the patches with the concept of auxiliary domains.
>>>
>>> Lu Baolu (8):
>>>    iommu: Add APIs for multiple domains per device
>>>    iommu/vt-d: Add multiple domains per device query
>>>    iommu/vt-d: Enable/disable multiple domains per device
>>>    iommu/vt-d: Attach/detach domains in auxiliary mode
>>>    iommu/vt-d: Return ID associated with an auxiliary domain
>>>    vfio/mdev: Add iommu place holders in mdev_device
>>>    vfio/type1: Add domain at(de)taching group helpers
>>>    vfio/type1: Handle different mdev isolation type
>>>
>>>   drivers/iommu/intel-iommu.c      | 315 
>>> ++++++++++++++++++++++++++++---
>>>   drivers/iommu/iommu.c            |  52 +++++
>>>   drivers/vfio/mdev/mdev_core.c    |  36 ++++
>>>   drivers/vfio/mdev/mdev_private.h |   2 +
>>>   drivers/vfio/vfio_iommu_type1.c  | 162 ++++++++++++++--
>>>   include/linux/intel-iommu.h      |  11 ++
>>>   include/linux/iommu.h            |  52 +++++
>>>   include/linux/mdev.h             |  23 +++
>>>   8 files changed, 618 insertions(+), 35 deletions(-)
>>>
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