Re: [Qemu-devel] [PATCH for-1.2 02/11] usb: Halt ep queue en cancel pending packets on a packet error

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

Hi,

On 09/01/2012 12:42 PM, Blue Swirl wrote:
> On Fri, Aug 31, 2012 at 2:19 PM, Gerd Hoffmann <kraxel@redhat.com> wrote:
>> From: Hans de Goede <hdegoede@redhat.com>
>>
>> For controllers which queue up more then 1 packet at a time, we must halt the
>> ep queue, and inside the controller code cancel all pending packets on an
>> error.
>>
>> There are multiple reasons for this:
>> 1) Guests expect the controllers to halt ep queues on error, so that they
>> get the opportunity to cancel transfers which the scheduled after the failing
>> one, before processing continues
>>
>> 2) Not cancelling queued up packets after a failed transfer also messes up
>> the controller state machine, in the case of EHCI causing the following
>> assert to trigger: "assert(p->qtdaddr == q->qtdaddr)" at hcd-ehci.c:2075
>>
>> 3) For bulk endpoints with pipelining enabled (redirection to a real USB
>> device), we must cancel all the transfers after this a failed one so that:
>> a) If they've completed already, they are not processed further causing more
>>     stalls to be reported, originating from the same failed transfer
>> b) If still in flight, they are cancelled before the guest does
>>     a clear stall, otherwise the guest and device can loose sync!
>>
>> Note this patch only touches the ehci and uhci controller changes, since AFAIK
>> no other controllers actually queue up multiple transfer. If I'm wrong on this
>> other controllers need to be updated too!
>>
>> Also note that this patch was heavily tested with the ehci code, where I had
>> a reproducer for a device causing a transfer to fail. The uhci code is not
>> tested with actually failing transfers and could do with a thorough review!
>>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
>> ---
>>   hw/usb.h          |    1 +
>>   hw/usb/core.c     |   35 ++++++++++++++++++++++++++++-------
>>   hw/usb/hcd-ehci.c |   13 +++++++++++++
>>   hw/usb/hcd-uhci.c |   16 ++++++++++++++++
>>   4 files changed, 58 insertions(+), 7 deletions(-)
>>
>> diff --git a/hw/usb.h b/hw/usb.h
>> index 432ccae..e574477 100644
>> --- a/hw/usb.h
>> +++ b/hw/usb.h
>> @@ -179,6 +179,7 @@ struct USBEndpoint {
>>       uint8_t ifnum;
>>       int max_packet_size;
>>       bool pipeline;
>> +    bool halted;
>>       USBDevice *dev;
>>       QTAILQ_HEAD(, USBPacket) queue;
>>   };
>> diff --git a/hw/usb/core.c b/hw/usb/core.c
>> index c7e5bc0..28b840e 100644
>> --- a/hw/usb/core.c
>> +++ b/hw/usb/core.c
>> @@ -382,12 +382,23 @@ int usb_handle_packet(USBDevice *dev, USBPacket *p)
>>       usb_packet_check_state(p, USB_PACKET_SETUP);
>>       assert(p->ep != NULL);
>>
>> +    /* Submitting a new packet clears halt */
>> +    if (p->ep->halted) {
>> +        assert(QTAILQ_EMPTY(&p->ep->queue));
>> +        p->ep->halted = false;
>> +    }
>> +
>>       if (QTAILQ_EMPTY(&p->ep->queue) || p->ep->pipeline) {
>>           ret = usb_process_one(p);
>>           if (ret == USB_RET_ASYNC) {
>>               usb_packet_set_state(p, USB_PACKET_ASYNC);
>>               QTAILQ_INSERT_TAIL(&p->ep->queue, p, queue);
>>           } else {
>> +            /*
>> +             * When pipelining is enabled usb-devices must always return async,
>> +             * otherwise packets can complete out of order!
>> +             */
>> +            assert(!p->ep->pipeline);
>>               p->result = ret;
>>               usb_packet_set_state(p, USB_PACKET_COMPLETE);
>>           }
>> @@ -399,6 +410,20 @@ int usb_handle_packet(USBDevice *dev, USBPacket *p)
>>       return ret;
>>   }
>>
>> +static void __usb_packet_complete(USBDevice *dev, USBPacket *p)
>
> Please check reserved namespaces in HACKING.

That talks about suffixes not prefixes.

Regards,

Hans