[dpdk-dev] [PATCH] vhost: don't stall if guest is slow

[dpdk-dev] [PATCH] vhost: don't stall if guest is slow

[Stephen Hemminger]

When guest is booting (or any othertime guest is busy) it is possible
for the small receive ring (256) to get full. If this happens the
vhost library should just return normally. It's current behavior
of logging just creates massive log spew/overflow which could even
act as a DoS attack against host.

Reported-by: Nathan Law <nlaw@brocade.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 lib/librte_vhost/vhost_rxtx.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
index 9322ce6..bbf3fac 100644
--- a/lib/librte_vhost/vhost_rxtx.c
+++ b/lib/librte_vhost/vhost_rxtx.c
@@ -510,17 +510,12 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
 
 			do {
 				avail_idx = *((volatile uint16_t *)&vq->avail->idx);
-				if (unlikely(res_cur_idx == avail_idx)) {
-					LOG_DEBUG(VHOST_DATA,
-						"(%"PRIu64") Failed "
-						"to get enough desc from "
-						"vring\n",
-						dev->device_fh);
+				if (unlikely(res_cur_idx == avail_idx))
 					goto merge_rx_exit;
-				} else {
-					update_secure_len(vq, res_cur_idx, &secure_len, &vec_idx);
-					res_cur_idx++;
-				}
+
+				update_secure_len(vq, res_cur_idx,
+						  &secure_len, &vec_idx);
+				res_cur_idx++;
 			} while (pkt_len > secure_len);
 
 			/* vq->last_used_idx_res is atomically updated. */
-- 
2.1.4

Re: [dpdk-dev] [PATCH] vhost: don't stall if guest is slow

[Yuanhan Liu]

On Mon, Dec 07, 2015 at 04:50:21PM -0800, Stephen Hemminger wrote:
> When guest is booting (or any othertime guest is busy) it is possible
> for the small receive ring (256) to get full. If this happens the
> vhost library should just return normally. It's current behavior
> of logging just creates massive log spew/overflow which could even
> act as a DoS attack against host.
> 
> Reported-by: Nathan Law <nlaw@brocade.com>
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>

Thanks.

	--yliu

Re: [dpdk-dev] [PATCH] vhost: don't stall if guest is slow

[Thomas Monjalon]

2015-12-08 10:23, Yuanhan Liu:
> On Mon, Dec 07, 2015 at 04:50:21PM -0800, Stephen Hemminger wrote:
> > When guest is booting (or any othertime guest is busy) it is possible
> > for the small receive ring (256) to get full. If this happens the
> > vhost library should just return normally. It's current behavior
> > of logging just creates massive log spew/overflow which could even
> > act as a DoS attack against host.
> > 
> > Reported-by: Nathan Law <nlaw@brocade.com>
> > Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> 
> Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>

Yuanhan, please what is your opinion about the balance benefit/risk
of this patch for 2.2?

Re: [dpdk-dev] [PATCH] vhost: don't stall if guest is slow

[Yuanhan Liu]

On Tue, Dec 08, 2015 at 03:30:43AM +0100, Thomas Monjalon wrote:
> 2015-12-08 10:23, Yuanhan Liu:
> > On Mon, Dec 07, 2015 at 04:50:21PM -0800, Stephen Hemminger wrote:
> > > When guest is booting (or any othertime guest is busy) it is possible
> > > for the small receive ring (256) to get full. If this happens the
> > > vhost library should just return normally. It's current behavior
> > > of logging just creates massive log spew/overflow which could even
> > > act as a DoS attack against host.
> > > 
> > > Reported-by: Nathan Law <nlaw@brocade.com>
> > > Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> > 
> > Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
> 
> Yuanhan, please what is your opinion about the balance benefit/risk
> of this patch for 2.2?

Thomas,

I agree with Stephen that such log is not necessary as it's a fair
normal case. However, I see no too much benefit/risk for 2.2: it
just removes a debug log after all.

	--yliu

Re: [dpdk-dev] [PATCH] vhost: don't stall if guest is slow

[Thomas Monjalon]

2015-12-08 11:12, Yuanhan Liu:
> On Tue, Dec 08, 2015 at 03:30:43AM +0100, Thomas Monjalon wrote:
> > 2015-12-08 10:23, Yuanhan Liu:
> > > On Mon, Dec 07, 2015 at 04:50:21PM -0800, Stephen Hemminger wrote:
> > > > When guest is booting (or any othertime guest is busy) it is possible
> > > > for the small receive ring (256) to get full. If this happens the
> > > > vhost library should just return normally. It's current behavior
> > > > of logging just creates massive log spew/overflow which could even
> > > > act as a DoS attack against host.
> > > > 
> > > > Reported-by: Nathan Law <nlaw@brocade.com>
> > > > Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> > > 
> > > Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
> > 
> > Yuanhan, please what is your opinion about the balance benefit/risk
> > of this patch for 2.2?
> 
> Thomas,
> 
> I agree with Stephen that such log is not necessary as it's a fair
> normal case. However, I see no too much benefit/risk for 2.2: it
> just removes a debug log after all.

Applied, thanks