Messages in this thread | | | Subject | Re: [PATCH v3 0/8] vfio/mdev: IOMMU aware mediated device | From | Xu Zaibo <> | Date | Mon, 15 Oct 2018 16:50:39 +0800 |
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Hi,
On 2018/10/15 10:48, Lu Baolu wrote: > Hi, > > On 10/13/2018 04:25 PM, Xu Zaibo wrote: >> Hi, >> >> On 2018/10/12 13:16, 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(). >> I just cannot understand here, how to get an iommu_device while I >> create mediated >> device in my parent device driver? > > When you are creating an mdev in your parent driver, you should know > which PCI device this mdev belonging to. >
So, generally, I can set the parent device as mdev's iommu_device? If that, however, Mdev already holds its parent device. So, I just figure what differences between Mdev's parent device and iommu_device are. >> >> And why not reuse the device of MDEV instread of adding a new device >> here? > > iommu_device in the mdev_device structure represents the PCI device > that represents this mdev in iommu's device scope. IOMMU is only aware > of pci devices, it's not aware of mdev device.
Could I understand like that: IOMMU can be aware of the parent device of Mdev? And more, I am doubting the necessary of iommu_device in Mdev.
Thanks, Zaibo
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