Comment 23 for bug 1635339

Cc: <email address hidden>
Signed-off-by: Gerd Hoffmann <email address hidden>
Reviewed-by: Marc-André Lureau <email address hidden>
Message-id: <email address hidden>
---
 hw/display/qxl.h | 1 +
 hw/display/qxl.c | 31 +++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/hw/display/qxl.h b/hw/display/qxl.h
index d2d49dd..77e5a36 100644
--- a/hw/display/qxl.h
+++ b/hw/display/qxl.h
@@ -40,6 +40,7 @@ typedef struct PCIQXLDevice {
     uint32_t cmdlog;

     uint32_t guest_bug;
+ Error *migration_blocker;

     enum qxl_mode mode;
     uint32_t cmdflags;
diff --git a/hw/display/qxl.c b/hw/display/qxl.c
index c31b293..9feae78 100644
--- a/hw/display/qxl.c
+++ b/hw/display/qxl.c
@@ -26,6 +26,7 @@
 #include "qemu/queue.h"
 #include "qemu/atomic.h"
 #include "sysemu/sysemu.h"
+#include "migration/migration.h"
 #include "trace.h"

 #include "qxl.h"
@@ -639,6 +640,30 @@ static int interface_get_command(QXLInstance *sin, struct QXLCommandExt *ext)
         qxl->guest_primary.commands++;
         qxl_track_command(qxl, ext);
         qxl_log_command(qxl, "cmd", ext);
+ {
+ /*
+ * Windows 8 drivers place qxl commands in the vram
+ * (instead of the ram) bar. We can't live migrate such a
+ * guest, so add a migration blocker in case we detect
+ * this, to avoid triggering the assert in pre_save().
+ *
+ * https://cgit.freedesktop.org/spice/win32/qxl-wddm-dod/commit/?id=f6e099db39e7d0787f294d5fd0dce328b5210faa
+ */
+ void *msg = qxl_phys2virt(qxl, ext->cmd.data, ext->group_id);
+ if (msg != NULL && (
+ msg < (void *)qxl->vga.vram_ptr ||
+ msg > ((void *)qxl->vga.vram_ptr + qxl->vga.vram_size))) {
+ if (!qxl->migration_blocker) {
+ Error *local_err = NULL;
+ error_setg(&qxl->migration_blocker,
+ "qxl: guest bug: command not in ram bar");
+ migrate_add_blocker(qxl->migration_blocker, &local_err);
+ if (local_err) {
+ error_report_err(local_err);
+ }
+ }
+ }
+ }
         trace_qxl_ring_command_get(qxl->id, qxl_mode_to_string(qxl->mode));
         return true;
     default:
@@ -1236,6 +1261,12 @@ static void qxl_hard_reset(PCIQXLDevice *d, int loadvm)
     qemu_spice_create_host_memslot(&d->ssd);
     qxl_soft_reset(d);

+ if (d->migration_blocker) {
+ migrate_del_blocker(d->migration_blocker);
+ error_free(d->migration_blocker);
+ d->migration_blocker = NULL;
+ }
+
     if (startstop) {
         qemu_spice_display_start();
     }
--
2.9.3