Re: [PATCH] ixgbe: fix crash caused by bulk allocation failure in vector pmd

[Thomas Monjalon <thomas.monjalon-pdR9zngts4EAvxtiuMwx3w@public.gmane.org>]

> > Since the introduction of vector PMD, a bug in ixgbe_rxq_rearm could
> > cause a crash. As long as the memory pool allocated to the RX queue
> > has mbufs available, there is no problem. After allocation of _all_
> > mbufs from the memory pool, previously returned mbufs by
> > rte_eth_rx_burst could be accessed by subsequent calls to the PMD and
> > could be returned by subsequent calls to rte_eth_rx_burst. From the
> > perspective of the application, the means that fields within the mbuf
> > could change and that previously allocated mbufs could appear multiple
> > times.
> > 
> > After failure of mbuf allocation, the dd bits should indicate that the
> > packets are not ready. For this, this patch adds code to reset the dd
> > bits in the first RTE_IXGBE_DESCS_PER_LOOP packets of the next
> > RTE_IXGBE_RXQ_REARM_THRESH packets only if the next
> > RTE_IXGBE_RXQ_REARM_THRESH packets that will be accessed contain
> > previously allocated packets.
> > 
> > Setting the bits is not enough. The bits are checked _after_ setting
> > the mbuf fields, thus a mechanism is needed to prevent the previously
> > used mbuf pointers from being accessed during the speculative load of
> > the mbuf fields. For this reason, not only the dd bits are reset, but
> > also the mbufs associated to those descriptors are set to point to a
> > "fake" mbuf.
> > 
> > Signed-off-by: Balazs Nemeth <balazs.nemeth-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> 
> Acked-by: Konstantin Ananyev <konstantin.ananyev-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

Applied

Thanks
-- 
Thomas