[Qemu-devel] [PATCH 1/9] ehci: Don't set seen to 0 when removing unseen queue-heads

[Hans de Goede <hdegoede@redhat.com>]

When removing unseen queue-heads from the async queue list, we should not
set the seen flag to 0, as this may cause them to be removed by
ehci_queues_rip_unused() during the next call to ehci_advance_async_state()
if the timer is late or running at a low frequency.

Note:
1) This *may* have caused the instant unlink / relinks described in commit
   9bc3a3a216e2689bfcdd36c3e079333bbdbf3ba0

2) Rather then putting more if-s inside ehci_queues_rip_unused, this patch
   instead introduces a new ehci_queues_rip_unseen function.

3) This patch also makes it save to call ehci_queues_rip_unseen() multiple
   times, which gets used in the folluw up patch titled:
   "ehci: Walk async schedule before and after migration"

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 hw/usb/hcd-ehci.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/hw/usb/hcd-ehci.c b/hw/usb/hcd-ehci.c
index 2f3e9c0..c5f2635 100644
--- a/hw/usb/hcd-ehci.c
+++ b/hw/usb/hcd-ehci.c
@@ -853,10 +853,10 @@ static EHCIQueue *ehci_find_queue_by_qh(EHCIState *ehci, uint32_t addr,
     return NULL;
 }
 
-static void ehci_queues_rip_unused(EHCIState *ehci, int async, int flush)
+static void ehci_queues_rip_unused(EHCIState *ehci, int async)
 {
     EHCIQueueHead *head = async ? &ehci->aqueues : &ehci->pqueues;
-    const char *warn = (async && !flush) ? "guest unlinked busy QH" : NULL;
+    const char *warn = async ? "guest unlinked busy QH" : NULL;
     uint64_t maxage = FRAME_TIMER_NS * ehci->maxframes * 4;
     EHCIQueue *q, *tmp;
 
@@ -866,13 +866,25 @@ static void ehci_queues_rip_unused(EHCIState *ehci, int async, int flush)
             q->ts = ehci->last_run_ns;
             continue;
         }
-        if (!flush && ehci->last_run_ns < q->ts + maxage) {
+        if (ehci->last_run_ns < q->ts + maxage) {
             continue;
         }
         ehci_free_queue(q, warn);
     }
 }
 
+static void ehci_queues_rip_unseen(EHCIState *ehci, int async)
+{
+    EHCIQueueHead *head = async ? &ehci->aqueues : &ehci->pqueues;
+    EHCIQueue *q, *tmp;
+
+    QTAILQ_FOREACH_SAFE(q, head, next, tmp) {
+        if (!q->seen) {
+            ehci_free_queue(q, NULL);
+        }
+    }
+}
+
 static void ehci_queues_rip_device(EHCIState *ehci, USBDevice *dev, int async)
 {
     EHCIQueueHead *head = async ? &ehci->aqueues : &ehci->pqueues;
@@ -1732,7 +1744,7 @@ static int ehci_state_waitlisthead(EHCIState *ehci,  int async)
         ehci_set_usbsts(ehci, USBSTS_REC);
     }
 
-    ehci_queues_rip_unused(ehci, async, 0);
+    ehci_queues_rip_unused(ehci, async);
 
     /*  Find the head of the list (4.9.1.1) */
     for(i = 0; i < MAX_QH; i++) {
@@ -2364,7 +2376,7 @@ static void ehci_advance_async_state(EHCIState *ehci)
          */
         if (ehci->usbcmd & USBCMD_IAAD) {
             /* Remove all unseen qhs from the async qhs queue */
-            ehci_queues_rip_unused(ehci, async, 1);
+            ehci_queues_rip_unseen(ehci, async);
             trace_usb_ehci_doorbell_ack();
             ehci->usbcmd &= ~USBCMD_IAAD;
             ehci_raise_irq(ehci, USBSTS_IAA);
@@ -2417,7 +2429,7 @@ static void ehci_advance_periodic_state(EHCIState *ehci)
         ehci_set_fetch_addr(ehci, async,entry);
         ehci_set_state(ehci, async, EST_FETCHENTRY);
         ehci_advance_state(ehci, async);
-        ehci_queues_rip_unused(ehci, async, 0);
+        ehci_queues_rip_unused(ehci, async);
         break;
 
     default:
-- 
1.7.12