blob: 495203ff221c3e4039557fffafa56b22d38882c3 [file] [log] [blame]
/* Everything the "lguest" userspace program needs to know. */
#include <linux/types.h>
* Drivers
* The Guest needs devices to do anything useful. Since we don't let it touch
* real devices (think of the damage it could do!) we provide virtual devices.
* We could emulate a PCI bus with various devices on it, but that is a fairly
* complex burden for the Host and suboptimal for the Guest, so we have our own
* simple lguest bus and we use "virtio" drivers. These drivers need a set of
* routines from us which will actually do the virtual I/O, but they handle all
* the net/block/console stuff themselves. This means that if we want to add
* a new device, we simply need to write a new virtio driver and create support
* for it in the Launcher: this code won't need to change.
* Virtio devices are also used by kvm, so we can simply reuse their optimized
* device drivers. And one day when everyone uses virtio, my plan will be
* complete. Bwahahahah!
* Devices are described by a simplified ID, a status byte, and some "config"
* bytes which describe this device's configuration. This is placed by the
* Launcher just above the top of physical memory:
struct lguest_device_desc {
/* The device type: console, network, disk etc. Type 0 terminates. */
__u8 type;
/* The number of virtqueues (first in config array) */
__u8 num_vq;
* The number of bytes of feature bits. Multiply by 2: one for host
* features and one for Guest acknowledgements.
__u8 feature_len;
/* The number of bytes of the config array after virtqueues. */
__u8 config_len;
/* A status byte, written by the Guest. */
__u8 status;
__u8 config[0];
* This is how we expect the device configuration field for a virtqueue
* to be laid out in config space.
struct lguest_vqconfig {
/* The number of entries in the virtio_ring */
__u16 num;
/* The interrupt we get when something happens. */
__u16 irq;
/* The page number of the virtio ring for this device. */
__u32 pfn;
/* Write command first word is a request. */
enum lguest_req
LHREQ_INITIALIZE, /* + base, pfnlimit, start */
LHREQ_GETDMA, /* No longer used */
LHREQ_IRQ, /* + irq */
LHREQ_BREAK, /* No longer used */
LHREQ_EVENTFD, /* + address, fd. */
* The alignment to use between consumer and producer parts of vring.
* x86 pagesize for historical reasons.