ref: a3cbab3dc2fd16ddbed40ecbe1d884e0bb4988f7
dir: /sys/src/9/xen/xengrant.c/
/* * Sharing page frames with other domains */ #include "u.h" #include "../port/lib.h" #include "mem.h" #include "dat.h" #include "fns.h" enum { Nframes = 1, // XXX don't increase this without setting up extra mappings in xengrant_init() }; static struct { Lock; ushort free; ushort *refs; } refalloc; static grant_entry_t *granttab; void xengrantinit(void) { gnttab_setup_table_t setup; ulong frames[Nframes]; int nrefs, i; setup.dom = DOMID_SELF; setup.nr_frames = Nframes; set_xen_guest_handle(setup.frame_list, frames); if (HYPERVISOR_grant_table_op(GNTTABOP_setup_table, &setup, 1) != 0 || setup.status != 0) panic("xen grant table setup"); granttab = (grant_entry_t*)mmumapframe(XENGRANTTAB, frames[0]); nrefs = Nframes * BY2PG / sizeof(grant_entry_t); refalloc.refs = (ushort*)malloc(nrefs*sizeof(ushort)); for (i = 0; i < nrefs; i++) refalloc.refs[i] = i-1; refalloc.free = nrefs-1; } static int allocref(void) { int ref; ilock(&refalloc); ref = refalloc.free; if (ref > 0) refalloc.free = refalloc.refs[ref]; iunlock(&refalloc); return ref; } static void freeref(int ref) { ilock(&refalloc); refalloc.refs[ref] = refalloc.free; refalloc.free = ref; iunlock(&refalloc); } int xengrant(domid_t domid, ulong frame, int flags) { int ref; grant_entry_t *gt; if ((ref = allocref()) < 0) panic("out of xengrant refs"); gt = &granttab[ref]; gt->frame = frame; gt->domid = domid; coherence(); gt->flags = flags; return ref; } int xengrantend(int ref) { grant_entry_t *gt; int frame; gt = &granttab[ref]; coherence(); if (gt->flags>F_accept_transfer) { if ((gt->flags>F_transfer_completed) == 0) panic("xengrantend transfer in progress"); } else { if (gt->flags&(GTF_reading|GTF_writing)) panic("xengrantend frame in use"); } coherence(); frame = gt->frame; gt->flags = GTF_invalid; freeref(ref); return frame; }