diff options
Diffstat (limited to 'kernel/Documentation/vfio.txt')
| -rw-r--r-- | kernel/Documentation/vfio.txt | 62 |
1 files changed, 59 insertions, 3 deletions
diff --git a/kernel/Documentation/vfio.txt b/kernel/Documentation/vfio.txt index 96978eced..1dd3fddfd 100644 --- a/kernel/Documentation/vfio.txt +++ b/kernel/Documentation/vfio.txt @@ -289,10 +289,12 @@ PPC64 sPAPR implementation note This implementation has some specifics: -1) Only one IOMMU group per container is supported as an IOMMU group -represents the minimal entity which isolation can be guaranteed for and -groups are allocated statically, one per a Partitionable Endpoint (PE) +1) On older systems (POWER7 with P5IOC2/IODA1) only one IOMMU group per +container is supported as an IOMMU table is allocated at the boot time, +one table per a IOMMU group which is a Partitionable Endpoint (PE) (PE is often a PCI domain but not always). +Newer systems (POWER8 with IODA2) have improved hardware design which allows +to remove this limitation and have multiple IOMMU groups per a VFIO container. 2) The hardware supports so called DMA windows - the PCI address range within which DMA transfer is allowed, any attempt to access address space @@ -385,6 +387,18 @@ The code flow from the example above should be slightly changed: .... + /* Inject EEH error, which is expected to be caused by 32-bits + * config load. + */ + pe_op.op = VFIO_EEH_PE_INJECT_ERR; + pe_op.err.type = EEH_ERR_TYPE_32; + pe_op.err.func = EEH_ERR_FUNC_LD_CFG_ADDR; + pe_op.err.addr = 0ul; + pe_op.err.mask = 0ul; + ioctl(container, VFIO_EEH_PE_OP, &pe_op); + + .... + /* When 0xFF's returned from reading PCI config space or IO BARs * of the PCI device. Check the PE's state to see if that has been * frozen. @@ -427,6 +441,48 @@ The code flow from the example above should be slightly changed: .... +5) There is v2 of SPAPR TCE IOMMU. It deprecates VFIO_IOMMU_ENABLE/ +VFIO_IOMMU_DISABLE and implements 2 new ioctls: +VFIO_IOMMU_SPAPR_REGISTER_MEMORY and VFIO_IOMMU_SPAPR_UNREGISTER_MEMORY +(which are unsupported in v1 IOMMU). + +PPC64 paravirtualized guests generate a lot of map/unmap requests, +and the handling of those includes pinning/unpinning pages and updating +mm::locked_vm counter to make sure we do not exceed the rlimit. +The v2 IOMMU splits accounting and pinning into separate operations: + +- VFIO_IOMMU_SPAPR_REGISTER_MEMORY/VFIO_IOMMU_SPAPR_UNREGISTER_MEMORY ioctls +receive a user space address and size of the block to be pinned. +Bisecting is not supported and VFIO_IOMMU_UNREGISTER_MEMORY is expected to +be called with the exact address and size used for registering +the memory block. The userspace is not expected to call these often. +The ranges are stored in a linked list in a VFIO container. + +- VFIO_IOMMU_MAP_DMA/VFIO_IOMMU_UNMAP_DMA ioctls only update the actual +IOMMU table and do not do pinning; instead these check that the userspace +address is from pre-registered range. + +This separation helps in optimizing DMA for guests. + +6) sPAPR specification allows guests to have an additional DMA window(s) on +a PCI bus with a variable page size. Two ioctls have been added to support +this: VFIO_IOMMU_SPAPR_TCE_CREATE and VFIO_IOMMU_SPAPR_TCE_REMOVE. +The platform has to support the functionality or error will be returned to +the userspace. The existing hardware supports up to 2 DMA windows, one is +2GB long, uses 4K pages and called "default 32bit window"; the other can +be as big as entire RAM, use different page size, it is optional - guests +create those in run-time if the guest driver supports 64bit DMA. + +VFIO_IOMMU_SPAPR_TCE_CREATE receives a page shift, a DMA window size and +a number of TCE table levels (if a TCE table is going to be big enough and +the kernel may not be able to allocate enough of physically contiguous memory). +It creates a new window in the available slot and returns the bus address where +the new window starts. Due to hardware limitation, the user space cannot choose +the location of DMA windows. + +VFIO_IOMMU_SPAPR_TCE_REMOVE receives the bus start address of the window +and removes it. + ------------------------------------------------------------------------------- [1] VFIO was originally an acronym for "Virtual Function I/O" in its |