Re: [PATCH 2/2] e1000e: make TX reentrant

[Li Qiang <liq3ea@gmail.com>]

Jason Wang <jasowang@redhat.com> 于2020年7月22日周三 下午4:58写道：
>
> In loopback mode, e1000e RX can DMA into TX doorbell which requires
> TX to be reentrant. This patch make e1000e's TX routine reentrant by
> introducing a per device boolean for recording whether or not a TX
> rountine is being called and return early.
>

Could we introduce a per-queue 'sending' variable just like the RX.
So we can do this in net core layer.

Thanks,
Li Qiang

> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
>  hw/net/e1000e_core.c | 8 ++++++++
>  hw/net/e1000e_core.h | 1 +
>  2 files changed, 9 insertions(+)
>
> diff --git a/hw/net/e1000e_core.c b/hw/net/e1000e_core.c
> index bcd186cac5..8126a644a5 100644
> --- a/hw/net/e1000e_core.c
> +++ b/hw/net/e1000e_core.c
> @@ -923,6 +923,12 @@ e1000e_start_xmit(E1000ECore *core, const E1000E_TxRing *txr)
>          return;
>      }
>
> +    if (core->sending) {
> +        return;
> +    }
> +
> +    core->sending = true;
> +
>      while (!e1000e_ring_empty(core, txi)) {
>          base = e1000e_ring_head_descr(core, txi);
>
> @@ -940,6 +946,8 @@ e1000e_start_xmit(E1000ECore *core, const E1000E_TxRing *txr)
>      if (!ide || !e1000e_intrmgr_delay_tx_causes(core, &cause)) {
>          e1000e_set_interrupt_cause(core, cause);
>      }
> +
> +    core->sending = false;
>  }
>
>  static bool
> diff --git a/hw/net/e1000e_core.h b/hw/net/e1000e_core.h
> index aee32f7e48..4679c1761f 100644
> --- a/hw/net/e1000e_core.h
> +++ b/hw/net/e1000e_core.h
> @@ -114,6 +114,7 @@ struct E1000Core {
>      void (*owner_start_recv)(PCIDevice *d);
>
>      uint32_t msi_causes_pending;
> +    bool sending;
>  };
>
>  void
> --
> 2.20.1
>