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