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[Andy Whitcroft <apw@xxxxxxxxxxxxx>]

** Tags added: kernel-hyper-v

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https://bugs.launchpad.net/bugs/1290151

Title:
  hyper-v: Hyper-V network broken for Trusty on Server 2008R2

Status in “linux” package in Ubuntu:
  Confirmed

Bug description:
  Due to a bug in the Hyper-V host verion 2008R2, we need to use a
  slightly smaller  receive buffer size, otherwise the buffer will not
  be accepted by the legacy hosts. Without this fix, the network driver
  will not load while hosting Trusty on Server 2008R2. The following
  patch addresses the problem:

  [PATCH net-next] hyperv: Change the receive buffer size for legacy
  hosts

  Due to a bug in the Hyper-V host verion 2008R2, we need to use a slightly smaller
   receive buffer size, otherwise the buffer will not be accepted by the legacy hosts.

   Signed-off-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
   ---
    drivers/net/hyperv/hyperv_net.h |    1 +
    drivers/net/hyperv/netvsc.c     |    6 +++++-
   2 files changed, 6 insertions(+), 1 deletions(-)

  diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
   index 39fc230..ea5f182 100644
   --- a/drivers/net/hyperv/hyperv_net.h
   +++ b/drivers/net/hyperv/hyperv_net.h
   @@ -516,6 +516,7 @@ struct nvsp_message {
    #define NETVSC_MTU 65536
    
    #define NETVSC_RECEIVE_BUFFER_SIZE              (1024*1024*16)  /* 16MB */
   +#define NETVSC_RECEIVE_BUFFER_SIZE_LEGACY      (1024*1024*15)  /* 15MB */
    
    #define NETVSC_RECEIVE_BUFFER_ID                0xcafe
    
   diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
   index 1a0280d..daddea2 100644
   --- a/drivers/net/hyperv/netvsc.c
   +++ b/drivers/net/hyperv/netvsc.c
   @@ -365,6 +365,11 @@ static int netvsc_connect_vsp(struct hv_device *device)
                    goto cleanup;
    
            /* Post the big receive buffer to NetVSP */
   +       if (net_device->nvsp_version <= NVSP_PROTOCOL_VERSION_2)
   +               net_device->recv_buf_size = NETVSC_RECEIVE_BUFFER_SIZE_LEGACY;
   +       else
   +               net_device->recv_buf_size = NETVSC_RECEIVE_BUFFER_SIZE;
   +
            ret = netvsc_init_recv_buf(device);
    
    cleanup:
   @@ -898,7 +903,6 @@ int netvsc_device_add(struct hv_device *device, void *additional_info)
            ndev = net_device->ndev;
    
            /* Initialize the NetVSC channel extension */
   -       net_device->recv_buf_size = NETVSC_RECEIVE_BUFFER_SIZE;
            spin_lock_init(&net_device->recv_pkt_list_lock);
    
            INIT_LIST_HEAD(&net_device->recv_pkt_list);
   -- 
   1.7.4.1

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