include/linux/lguest_launcher.h

   1 #ifndef _ASM_LGUEST_USER
   2 #define _ASM_LGUEST_USER
   3 /* Everything the "lguest" userspace program needs to know. */
   4 /* They can register up to 32 arrays of lguest_dma. */
   5 #define LGUEST_MAX_DMA          32
   6 /* At most we can dma 16 lguest_dma in one op. */
   7 #define LGUEST_MAX_DMA_SECTIONS 16
   8
   9 /* How many devices?  Assume each one wants up to two dma arrays per device. */
  10 #define LGUEST_MAX_DEVICES (LGUEST_MAX_DMA/2)
  11
  12 /*D:200
  13  * Lguest I/O
  14  *
  15  * The lguest I/O mechanism is the only way Guests can talk to devices.  There
  16  * are two hypercalls involved: SEND_DMA for output and BIND_DMA for input.  In
  17  * each case, "struct lguest_dma" describes the buffer: this contains 16
  18  * addr/len pairs, and if there are fewer buffer elements the len array is
  19  * terminated with a 0.
  20  *
  21  * I/O is organized by keys: BIND_DMA attaches buffers to a particular key, and
  22  * SEND_DMA transfers to buffers bound to particular key.  By convention, keys
  23  * correspond to a physical address within the device's page.  This means that
  24  * devices will never accidentally end up with the same keys, and allows the
  25  * Host use The Futex Trick (as we'll see later in our journey).
  26  *
  27  * SEND_DMA simply indicates a key to send to, and the physical address of the
  28  * "struct lguest_dma" to send.  The Host will write the number of bytes
  29  * transferred into the "struct lguest_dma"'s used_len member.
  30  *
  31  * BIND_DMA indicates a key to bind to, a pointer to an array of "struct
  32  * lguest_dma"s ready for receiving, the size of that array, and an interrupt
  33  * to trigger when data is received.  The Host will only allow transfers into
  34  * buffers with a used_len of zero: it then sets used_len to the number of
  35  * bytes transferred and triggers the interrupt for the Guest to process the
  36  * new input. */
  37 struct lguest_dma
  38 {
  39         /* 0 if free to be used, filled by the Host. */
  40         u32 used_len;
  41         unsigned long addr[LGUEST_MAX_DMA_SECTIONS];
  42         u16 len[LGUEST_MAX_DMA_SECTIONS];
  43 };
  44 /*:*/
  45
  46 /*D:460 This is the layout of a block device memory page.  The Launcher sets up
  47  * the num_sectors initially to tell the Guest the size of the disk.  The Guest
  48  * puts the type, sector and length of the request in the first three fields,
  49  * then DMAs to the Host.  The Host processes the request, sets up the result,
  50  * then DMAs back to the Guest. */
  51 struct lguest_block_page
  52 {
  53         /* 0 is a read, 1 is a write. */
  54         int type;
  55         u32 sector;     /* Offset in device = sector * 512. */
  56         u32 bytes;      /* Length expected to be read/written in bytes */
  57         /* 0 = pending, 1 = done, 2 = done, error */
  58         int result;
  59         u32 num_sectors; /* Disk length = num_sectors * 512 */
  60 };
  61
  62 /*D:520 The network device is basically a memory page where all the Guests on
  63  * the network publish their MAC (ethernet) addresses: it's an array of "struct
  64  * lguest_net": */
  65 struct lguest_net
  66 {
  67         /* Simply the mac address (with multicast bit meaning promisc). */
  68         unsigned char mac[6];
  69 };
  70 /*:*/
  71
  72 /* Where the Host expects the Guest to SEND_DMA console output to. */
  73 #define LGUEST_CONSOLE_DMA_KEY 0
  74
  75 /*D:010
  76  * Drivers
  77  *
  78  * The Guest needs devices to do anything useful.  Since we don't let it touch
  79  * real devices (think of the damage it could do!) we provide virtual devices.
  80  * We could emulate a PCI bus with various devices on it, but that is a fairly
  81  * complex burden for the Host and suboptimal for the Guest, so we have our own
  82  * "lguest" bus and simple drivers.
  83  *
  84  * Devices are described by an array of LGUEST_MAX_DEVICES of these structs,
  85  * placed by the Launcher just above the top of physical memory:
  86  */
  87 struct lguest_device_desc {
  88         /* The device type: console, network, disk etc. */
  89         u16 type;
  90 #define LGUEST_DEVICE_T_CONSOLE 1
  91 #define LGUEST_DEVICE_T_NET     2
  92 #define LGUEST_DEVICE_T_BLOCK   3
  93
  94         /* The specific features of this device: these depends on device type
  95          * except for LGUEST_DEVICE_F_RANDOMNESS. */
  96         u16 features;
  97 #define LGUEST_NET_F_NOCSUM             0x4000 /* Don't bother checksumming */
  98 #define LGUEST_DEVICE_F_RANDOMNESS      0x8000 /* IRQ is fairly random */
  99
 100         /* This is how the Guest reports status of the device: the Host can set
 101          * LGUEST_DEVICE_S_REMOVED to indicate removal, but the rest are only
 102          * ever manipulated by the Guest, and only ever set. */
 103         u16 status;
 104 /* 256 and above are device specific. */
 105 #define LGUEST_DEVICE_S_ACKNOWLEDGE     1 /* We have seen device. */
 106 #define LGUEST_DEVICE_S_DRIVER          2 /* We have found a driver */
 107 #define LGUEST_DEVICE_S_DRIVER_OK       4 /* Driver says OK! */
 108 #define LGUEST_DEVICE_S_REMOVED         8 /* Device has gone away. */
 109 #define LGUEST_DEVICE_S_REMOVED_ACK     16 /* Driver has been told. */
 110 #define LGUEST_DEVICE_S_FAILED          128 /* Something actually failed */
 111
 112         /* Each device exists somewhere in Guest physical memory, over some
 113          * number of pages. */
 114         u16 num_pages;
 115         u32 pfn;
 116 };
 117 /*:*/
 118
 119 /* Write command first word is a request. */
 120 enum lguest_req
 121 {
 122         LHREQ_INITIALIZE, /* + pfnlimit, pgdir, start, pageoffset */
 123         LHREQ_GETDMA, /* + addr (returns &lguest_dma, irq in ->used_len) */
 124         LHREQ_IRQ, /* + irq */
 125         LHREQ_BREAK, /* + on/off flag (on blocks until someone does off) */
 126 };
 127 #endif /* _ASM_LGUEST_USER */