include/linux/lguest_launcher.h

   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  */
  27 struct 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         /* The number of bytes of feature bits.  Multiply by 2: one for host
  33          * features and one for Guest acknowledgements. */
  34         __u8 feature_len;
  35         /* The number of bytes of the config array after virtqueues. */
  36         __u8 config_len;
  37         /* A status byte, written by the Guest. */
  38         __u8 status;
  39         __u8 config[0];
  40 };
  41
  42 /*D:135 This is how we expect the device configuration field for a virtqueue
  43  * to be laid out in config space. */
  44 struct lguest_vqconfig {
  45         /* The number of entries in the virtio_ring */
  46         __u16 num;
  47         /* The interrupt we get when something happens. */
  48         __u16 irq;
  49         /* The page number of the virtio ring for this device. */
  50         __u32 pfn;
  51 };
  52 /*:*/
  53
  54 /* Write command first word is a request. */
  55 enum lguest_req
  56 {
  57         LHREQ_INITIALIZE, /* + base, pfnlimit, start */
  58         LHREQ_GETDMA, /* No longer used */
  59         LHREQ_IRQ, /* + irq */
  60         LHREQ_BREAK, /* + on/off flag (on blocks until someone does off) */
  61 };
  62
  63 /* The alignment to use between consumer and producer parts of vring.
  64  * x86 pagesize for historical reasons. */
  65 #define LGUEST_VRING_ALIGN      4096
  66 #endif /* _LINUX_LGUEST_LAUNCHER */