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

[Jason Wang]

On 2020/7/22 下午7:24, Li Qiang wrote:
> 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.


It's kind of not easy since TX routine is called before the packet can 
reach network queue.

Thanks


> 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