hw/xen: Support mapping grant frames

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>

hw/i386/kvm/xen_gnttab.c

@@ -37,13 +37,26 @@ OBJECT_DECLARE_SIMPLE_TYPE(XenGnttabState, XEN_GNTTAB)
 #define XEN_PAGE_SHIFT 12
 #define XEN_PAGE_SIZE (1ULL << XEN_PAGE_SHIFT)
 
+#define ENTRIES_PER_FRAME_V1 (XEN_PAGE_SIZE / sizeof(grant_entry_v1_t))
+
 struct XenGnttabState {
     /*< private >*/
     SysBusDevice busdev;
     /*< public >*/
 
+    QemuMutex gnt_lock;
+
     uint32_t nr_frames;
     uint32_t max_frames;
+
+    union {
+        grant_entry_v1_t *v1;
+        /* Theoretically, v2 support could be added here. */
+    } entries;
+
+    MemoryRegion gnt_frames;
+    MemoryRegion *gnt_aliases;
+    uint64_t *gnt_frame_gpas;
 };
 
 struct XenGnttabState *xen_gnttab_singleton;
@@ -51,6 +64,7 @@ struct XenGnttabState *xen_gnttab_singleton;
 static void xen_gnttab_realize(DeviceState *dev, Error **errp)
 {
     XenGnttabState *s = XEN_GNTTAB(dev);
+    int i;
 
     if (xen_mode != XEN_EMULATE) {
         error_setg(errp, "Xen grant table support is for Xen emulation");
@@ -58,6 +72,38 @@ static void xen_gnttab_realize(DeviceState *dev, Error **errp)
     }
     s->nr_frames = 0;
     s->max_frames = kvm_xen_get_gnttab_max_frames();
+    memory_region_init_ram(&s->gnt_frames, OBJECT(dev), "xen:grant_table",
+                           XEN_PAGE_SIZE * s->max_frames, &error_abort);
+    memory_region_set_enabled(&s->gnt_frames, true);
+    s->entries.v1 = memory_region_get_ram_ptr(&s->gnt_frames);
+    memset(s->entries.v1, 0, XEN_PAGE_SIZE * s->max_frames);
+
+    /* Create individual page-sizes aliases for overlays */
+    s->gnt_aliases = (void *)g_new0(MemoryRegion, s->max_frames);
+    s->gnt_frame_gpas = (void *)g_new(uint64_t, s->max_frames);
+    for (i = 0; i < s->max_frames; i++) {
+        memory_region_init_alias(&s->gnt_aliases[i], OBJECT(dev),
+                                 NULL, &s->gnt_frames,
+                                 i * XEN_PAGE_SIZE, XEN_PAGE_SIZE);
+        s->gnt_frame_gpas[i] = INVALID_GPA;
+    }
+
+    qemu_mutex_init(&s->gnt_lock);
+
+    xen_gnttab_singleton = s;
+}
+
+static int xen_gnttab_post_load(void *opaque, int version_id)
+{
+    XenGnttabState *s = XEN_GNTTAB(opaque);
+    uint32_t i;
+
+    for (i = 0; i < s->nr_frames; i++) {
+        if (s->gnt_frame_gpas[i] != INVALID_GPA) {
+            xen_overlay_do_map_page(&s->gnt_aliases[i], s->gnt_frame_gpas[i]);
+        }
+    }
+    return 0;
 }
 
 static bool xen_gnttab_is_needed(void *opaque)
@@ -70,8 +116,11 @@ static const VMStateDescription xen_gnttab_vmstate = {
     .version_id = 1,
     .minimum_version_id = 1,
     .needed = xen_gnttab_is_needed,
+    .post_load = xen_gnttab_post_load,
     .fields = (VMStateField[]) {
         VMSTATE_UINT32(nr_frames, XenGnttabState),
+        VMSTATE_VARRAY_UINT32(gnt_frame_gpas, XenGnttabState, nr_frames, 0,
+                              vmstate_info_uint64, uint64_t),
         VMSTATE_END_OF_LIST()
     }
 };
@@ -106,6 +155,28 @@ type_init(xen_gnttab_register_types)
 
 int xen_gnttab_map_page(uint64_t idx, uint64_t gfn)
 {
-    return -ENOSYS;
+    XenGnttabState *s = xen_gnttab_singleton;
+    uint64_t gpa = gfn << XEN_PAGE_SHIFT;
+
+    if (!s) {
+        return -ENOTSUP;
+    }
+
+    if (idx >= s->max_frames) {
+        return -EINVAL;
+    }
+
+    QEMU_IOTHREAD_LOCK_GUARD();
+    QEMU_LOCK_GUARD(&s->gnt_lock);
+
+    xen_overlay_do_map_page(&s->gnt_aliases[idx], gpa);
+
+    s->gnt_frame_gpas[idx] = gpa;
+
+    if (s->nr_frames <= idx) {
+        s->nr_frames = idx + 1;
+    }
+
+    return 0;
 }
 

hw/i386/kvm/xen_overlay.c

@@ -49,7 +49,7 @@ struct XenOverlayState {
 
 struct XenOverlayState *xen_overlay_singleton;
 
-static void xen_overlay_do_map_page(MemoryRegion *page, uint64_t gpa)
+void xen_overlay_do_map_page(MemoryRegion *page, uint64_t gpa)
 {
     /*
      * Xen allows guests to map the same page as many times as it likes

hw/i386/kvm/xen_overlay.h

@@ -21,4 +21,6 @@ int xen_sync_long_mode(void);
 int xen_set_long_mode(bool long_mode);
 bool xen_is_long_mode(void);
 
+void xen_overlay_do_map_page(MemoryRegion *page, uint64_t gpa);
+
 #endif /* QEMU_XEN_OVERLAY_H */