[Qemu-devel] [PATCH 2/2] cdrom: Make disc change event visible to guests

[Amit Shah <amit.shah@redhat.com>]

Commit 93c8cfd9e67a62711b86f4c93747566885eb7928 tried to send a 'no
disc' event after a cdrom change so that guests notice a cd change event
between two 'cd present' states.  However, we don't go from

 'cd present' -> 'no cd' -> 'cd present'

as the SENSE_UNIT_ATTENTION sense_key is written over by the
ide_atapi_cmd_error() function.

So for the disc change event, let us ensure the error() function doesn't
trample over that value so we do get to report it the next time around.
Also, ensure we go from 'no cd' to 'cd present' state.

With this, older Linux guests (< 2.6.38) notice cd changes just fine.
For newer Linux guests (2.6.38+) cd change events break again and that
will be fixed by implementing the GET_EVENT_STATUS_NOTIFICATION command.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
---
 hw/ide/core.c     |   40 +++++++++++++++++++++++++++++++++++++---
 hw/ide/internal.h |    1 +
 2 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/hw/ide/core.c b/hw/ide/core.c
index d55d804..fd82439 100644
--- a/hw/ide/core.c
+++ b/hw/ide/core.c
@@ -1113,10 +1113,42 @@ static void ide_atapi_cmd(IDEState *s)
     }
     switch(s->io_buffer[0]) {
     case GPCMD_TEST_UNIT_READY:
-        if (bdrv_is_inserted(s->bs) && !s->cdrom_changed) {
-            ide_atapi_cmd_ok(s);
+        if (bdrv_is_inserted(s->bs)) {
+            int sense, asc;
+
+            sense = s->sense_key;
+            asc = s->asc;
+
+	    /*
+	     * First, check if there's any pending media change
+	     * notification to be given.
+	     *
+	     * We want the guest to notice an empty tray between a cd
+	     * change, so send one MEDIUM_NOT_PRESENT message after a
+	     * cd change.
+	     *
+	     * After we've sent that message, the guest will poke at
+	     * us again and send the UNIT_ATTENTION message then.
+	     * Once this is done, reset the UNIT_ATTENTION message to
+	     * ensure we don't keep repeating it.
+	     */
+            if (!s->media_change_notified) {
+                ide_atapi_cmd_error(s, SENSE_NOT_READY,
+                                    ASC_MEDIUM_NOT_PRESENT);
+                s->media_change_notified = 1;
+            } else if (s->cdrom_changed) {
+                s->sense_key = SENSE_UNIT_ATTENTION;
+                s->asc = ASC_MEDIUM_MAY_HAVE_CHANGED;
+                ide_atapi_cmd_ok(s);
+
+                s->cdrom_changed = 0;
+		sense = SENSE_NONE;
+            } else {
+                ide_atapi_cmd_ok(s);
+            }
+            s->sense_key = sense;
+            s->asc = asc;
         } else {
-            s->cdrom_changed = 0;
             ide_atapi_cmd_error(s, SENSE_NOT_READY,
                                 ASC_MEDIUM_NOT_PRESENT);
         }
@@ -1613,6 +1645,7 @@ static void cdrom_change_cb(void *opaque, int reason)
     s->sense_key = SENSE_UNIT_ATTENTION;
     s->asc = ASC_MEDIUM_MAY_HAVE_CHANGED;
     s->cdrom_changed = 1;
+    s->media_change_notified = 0;
     ide_set_irq(s->bus);
 }
 
@@ -2474,6 +2507,7 @@ static void ide_reset(IDEState *s)
     s->sense_key = 0;
     s->asc = 0;
     s->cdrom_changed = 0;
+    s->media_change_notified = 0;
     s->packet_transfer_size = 0;
     s->elementary_transfer_size = 0;
     s->io_buffer_index = 0;
diff --git a/hw/ide/internal.h b/hw/ide/internal.h
index d533fb6..5d58be4 100644
--- a/hw/ide/internal.h
+++ b/hw/ide/internal.h
@@ -411,6 +411,7 @@ struct IDEState {
     uint8_t sense_key;
     uint8_t asc;
     uint8_t cdrom_changed;
+    uint8_t media_change_notified;
     int packet_transfer_size;
     int elementary_transfer_size;
     int io_buffer_index;
-- 
1.7.4