Re: [PATCH v2 2/2] hw: usb: hcd-ohci: check for processed TD before retire

[Li Qiang]

P J P <ppandit@redhat.com> 于2020年9月16日周三 上午2:25写道：
>
> From: Prasad J Pandit <pjp@fedoraproject.org>

Reviewed-by: Li Qiang <liq3ea@gmail.com>

>
> While servicing OHCI transfer descriptors(TD), ohci_service_iso_td
> retires a TD if it has passed its time frame. It does not check if
> the TD was already processed once and holds an error code in TD_CC.
> It may happen if the TD list has a loop. Add check to avoid an
> infinite loop condition.
>
> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
> ---
>  hw/usb/hcd-ohci.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> Update v2: one patch for loop issue
>   -> https://lists.nongnu.org/archive/html/qemu-devel/2020-09/msg05145.html
>
> diff --git a/hw/usb/hcd-ohci.c b/hw/usb/hcd-ohci.c
> index 9dc59101f9..8b912e95d3 100644
> --- a/hw/usb/hcd-ohci.c
> +++ b/hw/usb/hcd-ohci.c
> @@ -691,6 +691,10 @@ static int ohci_service_iso_td(OHCIState *ohci, struct 
> ohci_ed *ed,
>             the next ISO TD of the same ED */
>          
> trace_usb_ohci_iso_td_relative_frame_number_big(relative_frame_number,
>                                                          frame_count);
> +        if (OHCI_CC_DATAOVERRUN == OHCI_BM(iso_td.flags, TD_CC)) {
> +            /* avoid infinite loop */
> +            return 1;
> +        }
>          OHCI_SET_BM(iso_td.flags, TD_CC, OHCI_CC_DATAOVERRUN);
>          ed->head &= ~OHCI_DPTR_MASK;
>          ed->head |= (iso_td.next & OHCI_DPTR_MASK);
> --
> 2.26.2
>