[MINIOS] Mapping page frames on demand added to the memory management.

Signed-off-by: Steven Smith <sos22@cam.ac.uk>
Signed-off-by: Grzegorz Milos <gm281@cam.ac.uk>

1 files changed, 158 insertions, 0 deletions

diff --git a/extras/mini-os/gnttab.c b/extras/mini-os/gnttab.c
new file mode 100644
index 0000000000..a405e0c072
--- /dev/null
+++ b/extras/mini-os/gnttab.c
@@ -0,0 +1,158 @@
+/* 
+ ****************************************************************************
+ * (C) 2006 - Cambridge University
+ ****************************************************************************
+ *
+ *        File: gnttab.c
+ *      Author: Steven Smith (sos22@cam.ac.uk) 
+ *     Changes: Grzegorz Milos (gm281@cam.ac.uk)
+ *              
+ *        Date: July 2006
+ * 
+ * Environment: Xen Minimal OS
+ * Description: Simple grant tables implementation. About as stupid as it's
+ *  possible to be and still work.
+ *
+ ****************************************************************************
+ */
+#include <os.h>
+#include <mm.h>
+#include <gnttab.h>
+
+#define NR_RESERVED_ENTRIES 8
+
+#define NR_GRANT_FRAMES 4
+#define NR_GRANT_ENTRIES (NR_GRANT_FRAMES * PAGE_SIZE / sizeof(grant_entry_t))
+#define GNTTAB_LIST_END (NR_GRANT_ENTRIES + 1)
+
+static grant_entry_t *gnttab_table;
+static grant_ref_t gnttab_list[NR_GRANT_ENTRIES];
+static grant_ref_t gnttab_free_head;
+
+static grant_ref_t
+get_free_entries(int count)
+{
+    grant_ref_t ref;
+    grant_ref_t head;
+
+    ref = head = gnttab_free_head;
+    while (count-- > 1)
+	head = gnttab_list[head];
+    gnttab_free_head = gnttab_list[head];
+    gnttab_list[head] = GNTTAB_LIST_END;
+    return ref;
+}
+
+static void
+put_free_entry(grant_ref_t gref)
+{
+    gnttab_list[gref] = gnttab_free_head;
+    gnttab_free_head = gref;
+}
+
+grant_ref_t
+gnttab_grant_access(domid_t domid, unsigned long frame, int readonly)
+{
+    grant_ref_t ref;
+
+    ref = get_free_entries(1);
+    gnttab_table[ref].frame = frame;
+    gnttab_table[ref].domid = domid;
+    wmb();
+    readonly *= GTF_readonly;
+    gnttab_table[ref].flags = GTF_permit_access | readonly;
+
+    return ref;
+}
+
+grant_ref_t
+gnttab_grant_transfer(domid_t domid, unsigned long pfn)
+{
+    grant_ref_t ref;
+
+    ref = get_free_entries(1);
+    gnttab_table[ref].frame = pfn;
+    gnttab_table[ref].domid = domid;
+    wmb();
+    gnttab_table[ref].flags = GTF_accept_transfer;
+
+    return ref;
+}
+
+int
+gnttab_end_access(grant_ref_t ref)
+{
+    u16 flags, nflags;
+
+    nflags = gnttab_table[ref].flags;
+    do {
+        if ((flags = nflags) & (GTF_reading|GTF_writing)) {
+            printk("WARNING: g.e. still in use!\n");
+            return 0;
+        }
+    } while ((nflags = synch_cmpxchg(&gnttab_table[ref].flags, flags, 0)) !=
+            flags);
+
+    put_free_entry(ref);
+    return 1;
+}
+
+unsigned long
+gnttab_end_transfer(grant_ref_t ref)
+{
+    unsigned long frame;
+    u16 flags;
+
+    while (!((flags = gnttab_table[ref].flags) & GTF_transfer_committed)) {
+        if (synch_cmpxchg(&gnttab_table[ref].flags, flags, 0) == flags) {
+            printk("Release unused transfer grant.\n");
+            put_free_entry(ref);
+            return 0;
+        }
+    }
+
+    /* If a transfer is in progress then wait until it is completed. */
+    while (!(flags & GTF_transfer_completed)) {
+        flags = gnttab_table[ref].flags;
+    }
+
+    /* Read the frame number /after/ reading completion status. */
+    rmb();
+    frame = gnttab_table[ref].frame;
+
+    put_free_entry(ref);
+
+    return frame;
+}
+
+grant_ref_t
+gnttab_alloc_and_grant(void **map)
+{
+    unsigned long mfn;
+    grant_ref_t gref;
+
+    *map = (void *)alloc_page();
+    mfn = virt_to_mfn(*map);
+    gref = gnttab_grant_access(0, mfn, 0);
+    return gref;
+}
+
+void
+init_gnttab(void)
+{
+    struct gnttab_setup_table setup;
+    unsigned long frames[NR_GRANT_FRAMES];
+    int i;
+
+    for (i = NR_RESERVED_ENTRIES; i < NR_GRANT_ENTRIES; i++)
+	gnttab_list[i] = i + 1;
+    gnttab_free_head = NR_RESERVED_ENTRIES;
+
+    setup.dom = DOMID_SELF;
+    setup.nr_frames = NR_GRANT_FRAMES;
+    set_xen_guest_handle(setup.frame_list, frames);
+
+    HYPERVISOR_grant_table_op(GNTTABOP_setup_table, &setup, 1);
+    gnttab_table = map_frames(frames, NR_GRANT_FRAMES);
+    printk("gnttab_table mapped at %p.\n", gnttab_table);
+}