From: Hans de Goede <hdego...@redhat.com> If the guest is using multiple transfers to try and keep the usb bus busy / used at maximum efficiency, currently we would see / do the following:
1) submit transfer 1 to the device 2) submit transfer 2 to the device 3) report transfer 1 completion to guest 4) report transfer 2 completion to guest 5) submit transfer 1 to the device 6) report transfer 1 completion to guest 7) submit transfer 2 to the device 8) report transfer 2 completion to guest etc. So after the initial submission we would effectively only have 1 transfer in flight, rather then 2. This is caused by us not checking the queue for addition of new transfers by the guest (ie the resubmission of a recently finished transfer), while waiting for a pending transfer to complete. This patch does add a check for this, changing the sequence to: 1) submit transfer 1 to the device 2) submit transfer 2 to the device 3) report transfer 1 completion to guest 4) submit transfer 1 to the device 5) report transfer 2 completion to guest 6) submit transfer 2 to the device etc. Thus keeping 2 transfers in flight (most of the time, and always 1), as intended by the guest. Signed-off-by: Hans de Goede <hdego...@redhat.com> Signed-off-by: Gerd Hoffmann <kra...@redhat.com> --- hw/usb/hcd-uhci.c | 16 +++++++++++++--- 1 files changed, 13 insertions(+), 3 deletions(-) diff --git a/hw/usb/hcd-uhci.c b/hw/usb/hcd-uhci.c index beeb3fd..a9e06ef 100644 --- a/hw/usb/hcd-uhci.c +++ b/hw/usb/hcd-uhci.c @@ -110,7 +110,7 @@ struct UHCIQueue { UHCIState *uhci; USBEndpoint *ep; QTAILQ_ENTRY(UHCIQueue) next; - QTAILQ_HEAD(, UHCIAsync) asyncs; + QTAILQ_HEAD(asyncs_head, UHCIAsync) asyncs; int8_t valid; }; @@ -843,15 +843,25 @@ static int uhci_handle_td(UHCIState *s, UHCIQueue *q, uint32_t qh_addr, } if (async) { - if (!async->done) - return TD_RESULT_ASYNC_CONT; if (queuing) { /* we are busy filling the queue, we are not prepared to consume completed packages then, just leave them in async state */ return TD_RESULT_ASYNC_CONT; } + if (!async->done) { + UHCI_TD last_td; + UHCIAsync *last = QTAILQ_LAST(&async->queue->asyncs, asyncs_head); + /* + * While we are waiting for the current td to complete, the guest + * may have added more tds to the queue. Note we re-read the td + * rather then caching it, as we want to see guest made changes! + */ + uhci_read_td(s, &last_td, last->td_addr); + uhci_queue_fill(async->queue, &last_td); + return TD_RESULT_ASYNC_CONT; + } uhci_async_unlink(async); goto done; } -- 1.7.1