I'm having trouble understanding how this works where
the Guest Device Model != Host. How do you inform the guest
where the device is mapped in its physical address space,
and handle GPA faults?
- Mario
On 7/3/2013 11:40 PM, Yoder Stuart-B08248 wrote:
> Version 2
> -VFIO_GROUP_GET_DEVICE_FD-- specified that the path is a sysfs path
> -VFIO_DEVICE_GET_INFO-- defined 2 flags instead of 1
> -deleted VFIO_DEVICE_GET_DEVTREE_INFO ioctl
> -VFIO_DEVICE_GET_REGION_INFO-- updated as per AlexW's suggestion,
> defined 5 new flags and associated structs
> -VFIO_DEVICE_GET_IRQ_INFO-- updated as per AlexW's suggestion,
> defined 1 new flag and associated struct
> -removed redundant example
>
> ------------------------------------------------------------------------------
> VFIO for Platform Devices
>
> The existing kernel interface for vfio-pci is pretty close to what is needed
> for platform devices:
> -mechanism to create a container
> -add groups/devices to a container
> -set the IOMMU model
> -map DMA regions
> -get an fd for a specific device, which allows user space to determine
> info about device regions (e.g. registers) and interrupt info
> -support for mmapping device regions
> -mechanism to set how interrupts are signaled
>
> Many platform device are simple and consist of a single register
> region and a single interrupt. For these types of devices the
> existing vfio interfaces should be sufficient.
>
> However, platform devices can get complicated-- logically represented
> as a device tree hierarchy of nodes. For devices with multiple regions
> and interrupts, new mechanisms are needed in vfio to correlate the
> regions/interrupts with the device tree structure that drivers use
> to determine the meaning of device resources.
>
> In some cases there are relationships between device, and devices
> reference other devices using phandle links. The kernel won't expose
> relationships between devices, but just exposes mappable register
> regions and interrupts.
>
> The changes needed for vfio are around some of the device tree
> related info that needs to be available with the device fd.
>
> 1. VFIO_GROUP_GET_DEVICE_FD
>
> User space knows by out-of-band means which device it is accessing
> and will call VFIO_GROUP_GET_DEVICE_FD passing a specific sysfs path
> to get the device information:
>
> fd = ioctl(group, VFIO_GROUP_GET_DEVICE_FD,
> "/sys/bus/platform/devices/ffe210000.usb"));
>
> 2. VFIO_DEVICE_GET_INFO
>
> The number of regions corresponds to the regions defined
> in "reg" and "ranges" in the device tree.
>
> Two new flags are added to struct vfio_device_info:
>
> #define VFIO_DEVICE_FLAGS_PLATFORM (1 << ?) /* A platform bus device */
> #define VFIO_DEVICE_FLAGS_DEVTREE (1 << ?) /* device tree info available */
>
> It is possible that there could be platform bus devices
> that are not in the device tree, so we use 2 flags to
> allow for that.
>
> If just VFIO_DEVICE_FLAGS_PLATFORM is set, it means
> that there are regions and IRQs but no device tree info
> available.
>
> If just VFIO_DEVICE_FLAGS_DEVTREE is set, it means
> there is device tree info available.
>
> 3. VFIO_DEVICE_GET_REGION_INFO
>
> For platform devices with multiple regions, information
> is needed to correlate the regions with the device
> tree structure that drivers use to determine the meaning
> of device resources.
>
> The VFIO_DEVICE_GET_REGION_INFO is extended to provide
> device tree information.
>
> The following information is needed:
> -the device tree path to the node corresponding to the
> region
> -whether it corresponds to a "reg" or "ranges" property
> -there could be multiple sub-regions per "reg" or "ranges" and
> the sub-index within the reg/ranges is needed
>
> There are 5 new flags added to vfio_region_info :
>
> struct vfio_region_info {
> __u32 argsz;
> __u32 flags;
> #define VFIO_REGION_INFO_FLAG_CACHEABLE (1 << ?)
> #define VFIO_DEVTREE_REGION_INFO_FLAG_REG (1 << ?)
> #define VFIO_DEVTREE_REGION_INFO_FLAG_RANGE (1 << ?)
> #define VFIO_DEVTREE_REGION_INFO_FLAG_INDEX (1 << ?)
> #define VFIO_DEVTREE_REGION_INFO_FLAG_PATH (1 << ?)
> __u32 index; /* Region index */
> __u32 resv; /* Reserved for alignment */
> __u64 size; /* Region size (bytes) */
> __u64 offset; /* Region offset from start of device fd */
> };
>
> VFIO_REGION_INFO_FLAG_CACHEABLE
> -if set indicates that the region must be mapped as cacheable
>
> VFIO_DEVTREE_REGION_INFO_FLAG_REG
> -if set indicates that the region corresponds to a "reg" property
> in the device tree representation of the device
>
> VFIO_DEVTREE_REGION_INFO_FLAG_RANGE
> -if set indicates that the region corresponds to a "ranges" property
> in the device tree representation of the device
>
> VFIO_DEVTREE_REGION_INFO_FLAG_INDEX
> -if set indicates that there is a dword aligned struct
> struct vfio_devtree_region_info_index appended to the
> end of vfio_region_info:
>
> struct vfio_devtree_region_info_index
> {
> u32 index;
> }
>
> A reg or ranges property may have multiple regsion. The index
> specifies the index within the "reg" or "ranges"
> that this region corresponds to.
>
> VFIO_DEVTREE_REGION_INFO_FLAG_PATH
> -if set indicates that there is a dword aligned struct
> struct vfio_devtree_info_path appended to the
> end of vfio_region_info:
>
> struct vfio_devtree_info_path
> {
> u32 len;
> u8 path[];
> }
>
> The path is the full path to the corresponding device
> tree node. The len field specifies the length of the
> path string.
>
> If multiple flags are set that indicate that there is
> an appended struct, the order of the flags indicates
> the order of the structs.
>
> argsz is set by the kernel specifying the total size of
> struct vfio_region_info and all appended structs.
>
> Suggested usage:
> -call VFIO_DEVICE_GET_REGION_INFO with argsz =
> sizeof(struct vfio_region_info)
> -realloc the buffer
> -call VFIO_DEVICE_GET_REGION_INFO again, and the appended
> structs will be returned
>
> 4. VFIO_DEVICE_GET_IRQ_INFO
>
> For platform devices with multiple interrupts that
> correspond to different subnodes in the device tree,
> information is needed to correlate the interrupts
> to the the device tree structure.
>
> The VFIO_DEVICE_GET_REGION_INFO is extended to provide
> device tree information.
>
> 1 new flag is added to vfio_irq_info :
>
> struct vfio_irq_info {
> __u32 argsz;
> __u32 flags;
> #define VFIO_DEVTREE_IRQ_INFO_FLAG_PATH (1 << ?)
> __u32 index; /* IRQ index */
> __u32 count; /* Number of IRQs within this index */
> };
>
> VFIO_DEVTREE_IRQ_INFO_FLAG_PATH
> -if set indicates that there is a dword aligned struct
> struct vfio_devtree_info_path appended to the
> end of vfio_irq_info :
>
> struct vfio_devtree_info_path
> {
> u32 len;
> u8 path[];
> }
>
> The path is the full path to the corresponding device
> tree node. The len field specifies the length of the
> path string.
>
> argsz is set by the kernel specifying the total size of
> struct vfio_region_info and all appended structs.
>
> 5. EXAMPLE 1
>
> Example, Freescale SATA controller:
>
> sata@220000 {
> compatible = "fsl,p2041-sata", "fsl,pq-sata-v2";
> reg = <0x220000 0x1000>;
> interrupts = <0x44 0x2 0x0 0x0>;
> };
>
> request to get device FD would look like:
> fd = ioctl(group, VFIO_GROUP_GET_DEVICE_FD, "/sys/bus/platform/devices/ffe220000.sata");
>
> The VFIO_DEVICE_GET_INFO ioctl would return:
> -1 region
> -1 interrupts
>
> The VFIO_DEVICE_GET_REGION_INFO ioctl would return:
> -for index 0:
> offset=0, size=0x10000 -- allows mmap of physical 0xffe220000
> flags = VFIO_DEVTREE_REGION_INFO_FLAG_REG |
> VFIO_DEVTREE_REGION_INFO_FLAG_PATH
> vfio_devtree_info_path
> len = 26
> path = "/soc@ffe000000/sata@220000"
>
> The VFIO_DEVICE_GET_IRQ_INFO ioctl would return:
> -for index 0:
> flags = VFIO_IRQ_INFO_EVENTFD |
> VFIO_IRQ_INFO_MASKABLE |
> VFIO_DEVTREE_IRQ_INFO_FLAG_PATH
> vfio_devtree_info_path
> len = 26
> path = "/soc@ffe000000/sata@220000"
>
> 6. EXAMPLE 2
>
> Example, Freescale DMA engine (modified to illustrate):
>
> dma@101300 {
> cell-index = <0x1>;
> ranges = <0x0 0x101100 0x200>;
> reg = <0x101300 0x4>;
> compatible = "fsl,eloplus-dma";
> #size-cells = <0x1>;
> #address-cells = <0x1>;
> fsl,liodn = <0xc6>;
>
> dma-channel@180 {
> interrupts = <0x23 0x2 0x0 0x0>;
> cell-index = <0x3>;
> reg = <0x180 0x80>;
> compatible = "fsl,eloplus-dma-channel";
> };
>
> dma-channel@100 {
> interrupts = <0x22 0x2 0x0 0x0>;
> cell-index = <0x2>;
> reg = <0x100 0x80>;
> compatible = "fsl,eloplus-dma-channel";
> };
>
> };
>
> request to get device FD would look like:
> fd = ioctl(group, VFIO_GROUP_GET_DEVICE_FD, "/sys/bus/platform/devices/ffe101300.dma");
>
> The VFIO_DEVICE_GET_INFO ioctl would return:
> -2 regions
> -2 interrupts
>
> The VFIO_DEVICE_GET_REGION_INFO ioctl would return:
> -for index 0:
> offset=0x100, size=0x200 -- allows mmap of physical 0xffe101100
> flags = VFIO_DEVTREE_REGION_INFO_FLAG_RANGES |
> VFIO_DEVTREE_REGION_INFO_FLAG_PATH
> vfio_devtree_info_path
> len = 25
> path = "/soc@ffe000000/dma@101300"
>
> -for index 1:
> offset=0x300, size=0x4 -- allows mmap of physical 0xffe101300
> flags = VFIO_DEVTREE_REGION_INFO_FLAG_REG |
> VFIO_DEVTREE_REGION_INFO_FLAG_PATH
> vfio_devtree_info_path
> len = 25
> path = "/soc@ffe000000/dma@101300"
>
> The VFIO_DEVICE_GET_IRQ_INFO ioctl would return:
> -for index 0:
> flags = VFIO_IRQ_INFO_EVENTFD |
> VFIO_IRQ_INFO_MASKABLE |
> VFIO_DEVTREE_IRQ_INFO_FLAG_PATH
> vfio_devtree_info_path
> len = 41
> path = "/soc@ffe000000/dma@101300/dma-channel@180"
>
> -for index 0:
> flags = VFIO_IRQ_INFO_EVENTFD |
> VFIO_IRQ_INFO_MASKABLE |
> VFIO_DEVTREE_IRQ_INFO_FLAG_PATH
> vfio_devtree_info_path
> len = 41
> path = "/soc@ffe000000/dma@101300/dma-channel@100"
>
>
> Regards,
> Stuart
>
>
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