From: "Wang, Zhihong" <zhihong.wang@intel.com>
To: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
"maxime.coquelin@redhat.com" <maxime.coquelin@redhat.com>,
"thomas.monjalon@6wind.com" <thomas.monjalon@6wind.com>,
"stable@dpdk.org" <stable@dpdk.org>
Subject: Re: [dpdk-stable] [PATCH v4 1/6] vhost: fix windows vm hang
Date: Mon, 5 Sep 2016 05:25:31 +0000 [thread overview]
Message-ID: <8F6C2BD409508844A0EFC19955BE09414E70B93E@SHSMSX103.ccr.corp.intel.com> (raw)
In-Reply-To: <20160905052446.GP7328@yliu-dev.sh.intel.com>
> -----Original Message-----
> From: Yuanhan Liu [mailto:yuanhan.liu@linux.intel.com]
> Sent: Monday, September 5, 2016 1:25 PM
> To: Wang, Zhihong <zhihong.wang@intel.com>
> Cc: dev@dpdk.org; maxime.coquelin@redhat.com;
> yuanhan.liu@linux.intel.com; thomas.monjalon@6wind.com;
> stable@dpdk.org
> Subject: Re: [dpdk-stable] [PATCH v4 1/6] vhost: fix windows vm hang
>
> On Mon, Aug 29, 2016 at 11:35:59PM -0400, Zhihong Wang wrote:
> > This patch fixes a Windows VM compatibility issue in DPDK 16.07 vhost
> code,
> > which causes the guest to hang once any packets are enqueued when
> mrg_rxbuf
> > is turned on.
>
> This commit log lacks two important pieces: why does the hang happen and
> how does your patch fix it.
Okay, I'll add it in v5.
>
> > How to test?
> >
> > 1. Start testpmd in the host with a vhost port.
> >
> > 2. Start a Windows VM image with qemu and connect to the vhost port.
> >
> > 3. Start io forwarding with tx_first in host testpmd.
> >
> > For 16.07 code, the Windows VM will hang once any packets are enqueued.
> >
> > Cc: <stable@dpdk.org>
> > Signed-off-by: Zhihong Wang <zhihong.wang@intel.com>
> > ---
> > lib/librte_vhost/vhost_rxtx.c | 17 ++++++++++++-----
> > 1 file changed, 12 insertions(+), 5 deletions(-)
> >
> > diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
> > index 08a73fd..5806f99 100644
> > --- a/lib/librte_vhost/vhost_rxtx.c
> > +++ b/lib/librte_vhost/vhost_rxtx.c
> > @@ -384,6 +384,8 @@ copy_mbuf_to_desc_mergeable(struct virtio_net
> *dev, struct vhost_virtqueue *vq,
> > uint16_t start_idx = vq->last_used_idx;
> > uint16_t cur_idx = start_idx;
> > uint64_t desc_addr;
> > + uint32_t desc_chain_head;
> > + uint32_t desc_chain_len;
>
> What's the point of introducing "desc_chain_len"? It has the same value
> of desc_offset.
No it's not, desc_offset is the offset of the current desc only.
That's where the old code goes wrong.
If you take a look at the virtio spec:
/* le32 is used here for ids for padding reasons. */
struct vring_used_elem {
/* Index of start of used descriptor chain. */
le32 id;
/* Total length of the descriptor chain which was written to. */
le32 len;
};
>
> --yliu
next prev parent reply other threads:[~2016-09-05 5:25 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1471319402-112998-1-git-send-email-zhihong.wang@intel.com>
[not found] ` <1472528164-54296-1-git-send-email-zhihong.wang@intel.com>
2016-08-30 3:35 ` Zhihong Wang
2016-09-05 5:24 ` Yuanhan Liu
2016-09-05 5:25 ` Wang, Zhihong [this message]
2016-09-05 5:40 ` Yuanhan Liu
[not found] ` <1473392368-84903-1-git-send-email-zhihong.wang@intel.com>
2016-09-09 3:39 ` [dpdk-stable] [PATCH v5 " Zhihong Wang
[not found] ` <1474336817-22683-1-git-send-email-zhihong.wang@intel.com>
2016-09-20 2:00 ` [dpdk-stable] [PATCH v6 " Zhihong Wang
2016-10-13 6:18 ` Yuanhan Liu
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