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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