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

[Jason Wang]

On 2020/7/23 下午6:36, Peter Maydell wrote:
> On Wed, 22 Jul 2020 at 10:00, Jason Wang <jasowang@redhat.com> wrote:
> > 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.
> >
> > Signed-off-by: Jason Wang <jasowang@redhat.com>
> > ---
> This feels like a sticking-plaster fix that's not really in the
> right place... It stops us from calling back into
> e1000e_start_xmit(), but it doesn't prevent a DMA request
> from touching other device registers that update state in
> the E100ECore struct that the transmit code is not expecting
> to change.


Right, so we can track the mr owner and fail the memory access if 
there's another mr transaction in memory core: 
memory_region_dispatch_read() and memory_region_dispatch_write().

But what's more interesting is that some device uses bh for the doorbell 
which may require more thought...

Thanks


> thanks
> -- PMM