kernel-ark/include/linux/lguest_launcher.h
Rusty Russell a586d4f601 virtio: simplify config mechanism.
Previously we used a type/len pair within the config space, but this
seems overkill.  We now simply define a structure which represents the
layout in the config space: the config space can now only be extended
at the end.

The main driver-visible changes:
1) We indicate what fields are present with an explicit feature bit.
2) Virtqueues are explicitly numbered, and not in the config space.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2008-02-04 23:49:57 +11:00

59 lines
2.1 KiB
C

#ifndef _LINUX_LGUEST_LAUNCHER
#define _LINUX_LGUEST_LAUNCHER
/* Everything the "lguest" userspace program needs to know. */
#include <linux/types.h>
/*D:010
* 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.
*
* 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];
};
/*D:135 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, pgdir, start */
LHREQ_GETDMA, /* No longer used */
LHREQ_IRQ, /* + irq */
LHREQ_BREAK, /* + on/off flag (on blocks until someone does off) */
};
#endif /* _LINUX_LGUEST_LAUNCHER */