netdev - Re: [PATCH net] vhost: correctly check the iova range when waking virtqueue

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Date:   Fri, 24 Aug 2018 17:36:35 +0800
From:   Peter Xu <peterx@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     mst@...hat.com, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] vhost: correctly check the iova range when waking
 virtqueue

On Fri, Aug 24, 2018 at 04:53:13PM +0800, Jason Wang wrote:
> We don't wakeup the virtqueue if the first byte of pending iova range
> is the last byte of the range we just got updated. This will lead a
> virtqueue to wait for IOTLB updating forever. Fixing by correct the
> check and wake up the virtqueue in this case.
> 
> Fixes: 6b1e6cc7855b ("vhost: new device IOTLB API")
> Reported-by: Peter Xu <peterx@...hat.com>
> Signed-off-by: Jason Wang <jasowang@...hat.com>

Without this patch, this command will trigger the IO hang merely every
time from host to guest:

  netperf -H 1.2.3.4 -l 5 -t TCP_RR -- -b 100

After applying, I can run it 10 times continuously without a problem.

Reviewed-by: Peter Xu <peterx@...hat.com>
Tested-by: Peter Xu <peterx@...hat.com>

Thanks,

-- 
Peter Xu