linux/include/linux/lguest_launcher.h
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   1#ifndef _LINUX_LGUEST_LAUNCHER
   2#define _LINUX_LGUEST_LAUNCHER
   3/* Everything the "lguest" userspace program needs to know. */
   4#include <linux/types.h>
   5
   6/*D:010
   7 * Drivers
   8 *
   9 * The Guest needs devices to do anything useful.  Since we don't let it touch
  10 * real devices (think of the damage it could do!) we provide virtual devices.
  11 * We could emulate a PCI bus with various devices on it, but that is a fairly
  12 * complex burden for the Host and suboptimal for the Guest, so we have our own
  13 * simple lguest bus and we use "virtio" drivers.  These drivers need a set of
  14 * routines from us which will actually do the virtual I/O, but they handle all
  15 * the net/block/console stuff themselves.  This means that if we want to add
  16 * a new device, we simply need to write a new virtio driver and create support
  17 * for it in the Launcher: this code won't need to change.
  18 *
  19 * Virtio devices are also used by kvm, so we can simply reuse their optimized
  20 * device drivers.  And one day when everyone uses virtio, my plan will be
  21 * complete.  Bwahahahah!
  22 *
  23 * Devices are described by a simplified ID, a status byte, and some "config"
  24 * bytes which describe this device's configuration.  This is placed by the
  25 * Launcher just above the top of physical memory:
  26 */
  27struct lguest_device_desc {
  28        /* The device type: console, network, disk etc.  Type 0 terminates. */
  29        __u8 type;
  30        /* The number of virtqueues (first in config array) */
  31        __u8 num_vq;
  32        /*
  33         * The number of bytes of feature bits.  Multiply by 2: one for host
  34         * features and one for Guest acknowledgements.
  35         */
  36        __u8 feature_len;
  37        /* The number of bytes of the config array after virtqueues. */
  38        __u8 config_len;
  39        /* A status byte, written by the Guest. */
  40        __u8 status;
  41        __u8 config[0];
  42};
  43
  44/*D:135
  45 * This is how we expect the device configuration field for a virtqueue
  46 * to be laid out in config space.
  47 */
  48struct lguest_vqconfig {
  49        /* The number of entries in the virtio_ring */
  50        __u16 num;
  51        /* The interrupt we get when something happens. */
  52        __u16 irq;
  53        /* The page number of the virtio ring for this device. */
  54        __u32 pfn;
  55};
  56/*:*/
  57
  58/* Write command first word is a request. */
  59enum lguest_req
  60{
  61        LHREQ_INITIALIZE, /* + base, pfnlimit, start */
  62        LHREQ_GETDMA, /* No longer used */
  63        LHREQ_IRQ, /* + irq */
  64        LHREQ_BREAK, /* No longer used */
  65        LHREQ_EVENTFD, /* + address, fd. */
  66};
  67
  68/*
  69 * The alignment to use between consumer and producer parts of vring.
  70 * x86 pagesize for historical reasons.
  71 */
  72#define LGUEST_VRING_ALIGN      4096
  73#endif /* _LINUX_LGUEST_LAUNCHER */
  74
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