import xen 32 bit paravirtual kernel from /n/sources/xen.

1 files changed, 100 insertions, 0 deletions

diff --git a/sys/src/9/xen/xengrant.c b/sys/src/9/xen/xengrant.c
new file mode 100644
index 000000000..d4e5500e6
--- /dev/null
+++ b/sys/src/9/xen/xengrant.c
@@ -0,0 +1,100 @@
+/*
+ * 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&GTF_accept_transfer) {
+		if ((gt->flags&GTF_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;
+}