sys/src/9/xen/xengrant.c

   1 /*
   2  * Sharing page frames with other domains
   3  */
   4 #include        "u.h"
   5 #include        "../port/lib.h"
   6 #include        "mem.h"
   7 #include        "dat.h"
   8 #include        "fns.h"
   9
  10 enum {
  11         Nframes = 1,    // XXX don't increase this without setting up extra mappings in xengrant_init()
  12 };
  13
  14 static struct {
  15         Lock;
  16         ushort free;
  17         ushort *refs;
  18 } refalloc;
  19
  20 static grant_entry_t *granttab;
  21
  22 void
  23 xengrantinit(void)
  24 {
  25         gnttab_setup_table_t setup;
  26         ulong frames[Nframes];
  27         int nrefs, i;
  28
  29         setup.dom = DOMID_SELF;
  30         setup.nr_frames = Nframes;
  31         set_xen_guest_handle(setup.frame_list, frames);
  32         if (HYPERVISOR_grant_table_op(GNTTABOP_setup_table, &setup, 1) != 0 || setup.status != 0)
  33                 panic("xen grant table setup");
  34         granttab = (grant_entry_t*)mmumapframe(XENGRANTTAB, frames[0]);
  35         nrefs = Nframes * BY2PG / sizeof(grant_entry_t);
  36         refalloc.refs = (ushort*)malloc(nrefs*sizeof(ushort));
  37         for (i = 0; i < nrefs; i++)
  38                 refalloc.refs[i] = i-1;
  39         refalloc.free = nrefs-1;
  40 }
  41
  42 static int
  43 allocref(void)
  44 {
  45         int ref;
  46
  47         ilock(&refalloc);
  48         ref = refalloc.free;
  49         if (ref > 0)
  50                 refalloc.free = refalloc.refs[ref];
  51         iunlock(&refalloc);
  52         return ref;
  53 }
  54
  55 static void
  56 freeref(int ref)
  57 {
  58         ilock(&refalloc);
  59         refalloc.refs[ref] = refalloc.free;
  60         refalloc.free = ref;
  61         iunlock(&refalloc);
  62 }
  63
  64 int
  65 xengrant(domid_t domid, ulong frame, int flags)
  66 {
  67         int ref;
  68         grant_entry_t *gt;
  69
  70         if ((ref = allocref()) < 0)
  71                 panic("out of xengrant refs");
  72         gt = &granttab[ref];
  73         gt->frame = frame;
  74         gt->domid = domid;
  75         coherence();
  76         gt->flags = flags;
  77         return ref;
  78 }
  79
  80 int
  81 xengrantend(int ref)
  82 {
  83         grant_entry_t *gt;
  84         int frame;
  85
  86         gt = &granttab[ref];
  87         coherence();
  88         if (gt->flags&GTF_accept_transfer) {
  89                 if ((gt->flags&GTF_transfer_completed) == 0)
  90                         panic("xengrantend transfer in progress");
  91         } else {
  92                 if (gt->flags&(GTF_reading|GTF_writing))
  93                         panic("xengrantend frame in use");
  94         }
  95         coherence();
  96         frame = gt->frame;
  97         gt->flags = GTF_invalid;
  98         freeref(ref);
  99         return frame;
 100 }