Merge tag 'vfio-v3.11' of git://github.com/awilliam/linux-vfio

[cascardo/linux.git] / Documentation / vfio.txt

diff --git a/Documentation/vfio.txt b/Documentation/vfio.txt
index 8eda363..d7993dc 100644 (file)
--- a/Documentation/vfio.txt
+++ b/Documentation/vfio.txt
@@ -172,12 +172,12 @@ group and can access them as follows:
        struct vfio_device_info device_info = { .argsz = sizeof(device_info) };
 
        /* Create a new container */
-       container = open("/dev/vfio/vfio, O_RDWR);
+       container = open("/dev/vfio/vfio", O_RDWR);
 
        if (ioctl(container, VFIO_GET_API_VERSION) != VFIO_API_VERSION)
                /* Unknown API version */
 
-       if (!ioctl(container, VFIO_CHECK_EXTENSION, VFIO_X86_IOMMU))
+       if (!ioctl(container, VFIO_CHECK_EXTENSION, VFIO_TYPE1_IOMMU))
                /* Doesn't support the IOMMU driver we want. */
 
        /* Open the group */
@@ -193,7 +193,7 @@ group and can access them as follows:
        ioctl(group, VFIO_GROUP_SET_CONTAINER, &container);
 
        /* Enable the IOMMU model we want */
-       ioctl(container, VFIO_SET_IOMMU, VFIO_X86_IOMMU)
+       ioctl(container, VFIO_SET_IOMMU, VFIO_TYPE1_IOMMU)
 
        /* Get addition IOMMU info */
        ioctl(container, VFIO_IOMMU_GET_INFO, &iommu_info);
@@ -283,6 +283,69 @@ a direct pass through for VFIO_DEVICE_* ioctls.  The read/write/mmap
 interfaces implement the device region access defined by the device's
 own VFIO_DEVICE_GET_REGION_INFO ioctl.
 
+
+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)
+(PE is often a PCI domain but not always).
+
+2) The hardware supports so called DMA windows - the PCI address range
+within which DMA transfer is allowed, any attempt to access address space
+out of the window leads to the whole PE isolation.
+
+3) PPC64 guests are paravirtualized but not fully emulated. There is an API
+to map/unmap pages for DMA, and it normally maps 1..32 pages per call and
+currently there is no way to reduce the number of calls. In order to make things
+faster, the map/unmap handling has been implemented in real mode which provides
+an excellent performance which has limitations such as inability to do
+locked pages accounting in real time.
+
+So 3 additional ioctls have been added:
+
+       VFIO_IOMMU_SPAPR_TCE_GET_INFO - returns the size and the start
+               of the DMA window on the PCI bus.
+
+       VFIO_IOMMU_ENABLE - enables the container. The locked pages accounting
+               is done at this point. This lets user first to know what
+               the DMA window is and adjust rlimit before doing any real job.
+
+       VFIO_IOMMU_DISABLE - disables the container.
+
+
+The code flow from the example above should be slightly changed:
+
+       .....
+       /* Add the group to the container */
+       ioctl(group, VFIO_GROUP_SET_CONTAINER, &container);
+
+       /* Enable the IOMMU model we want */
+       ioctl(container, VFIO_SET_IOMMU, VFIO_SPAPR_TCE_IOMMU)
+
+       /* Get addition sPAPR IOMMU info */
+       vfio_iommu_spapr_tce_info spapr_iommu_info;
+       ioctl(container, VFIO_IOMMU_SPAPR_TCE_GET_INFO, &spapr_iommu_info);
+
+       if (ioctl(container, VFIO_IOMMU_ENABLE))
+               /* Cannot enable container, may be low rlimit */
+
+       /* Allocate some space and setup a DMA mapping */
+       dma_map.vaddr = mmap(0, 1024 * 1024, PROT_READ | PROT_WRITE,
+                            MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
+
+       dma_map.size = 1024 * 1024;
+       dma_map.iova = 0; /* 1MB starting at 0x0 from device view */
+       dma_map.flags = VFIO_DMA_MAP_FLAG_READ | VFIO_DMA_MAP_FLAG_WRITE;
+
+       /* Check here is .iova/.size are within DMA window from spapr_iommu_info */
+
+       ioctl(container, VFIO_IOMMU_MAP_DMA, &dma_map);
+       .....
+
 -------------------------------------------------------------------------------
 
 [1] VFIO was originally an acronym for "Virtual Function I/O" in its