hv_netvsc: Add support to set MTU reservation from guest side

When packet encapsulation is in use, the MTU needs to be reduced for
headroom reservation.
The existing code takes the updated MTU value only from the host side.
But vSwitch extensions, such as Open vSwitch, require the flexibility
to change the MTU to different values from within a guest during the
lifecycle of a vNIC, when the encapsulation protocol is changed. The
patch supports this kind of MTU changes.

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit f9cbce34c34bcc05ea0dd78c8999bfe88b5b6b86)

Orabug: 21886720
Signed-off-by: Jason Luo <zhangqing.luo@oracle.com>

diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
index fc3055dc6dc149eacedea59e1fc5268d544af201..fe71fc9febb2d7404daedff12a3f92b6f9808ee2 100644 (file)
--- a/drivers/net/hyperv/hyperv_net.h
+++ b/drivers/net/hyperv/hyperv_net.h
@@ -589,6 +589,7 @@ struct nvsp_message {
 
 
 #define NETVSC_MTU 65536
+#define NETVSC_MTU_MIN 68
 
 #define NETVSC_RECEIVE_BUFFER_SIZE             (1024*1024*16)  /* 16MB */
 #define NETVSC_RECEIVE_BUFFER_SIZE_LEGACY      (1024*1024*15)  /* 15MB */

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index fddd3f010c02174f40f642f9d89e3c152a3e889f..e91329d5d2becada23d58594b0d94955961d28dc 100644 (file)
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -743,8 +743,7 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
        if (nvdev->nvsp_version >= NVSP_PROTOCOL_VERSION_2)
                limit = NETVSC_MTU - ETH_HLEN;
 
-       /* Hyper-V hosts don't support MTU < ETH_DATA_LEN (1500) */
-       if (mtu < ETH_DATA_LEN || mtu > limit)
+       if (mtu < NETVSC_MTU_MIN || mtu > limit)
                return -EINVAL;
 
        nvdev->start_remove = true;

diff --git a/drivers/net/hyperv/rndis_filter.c b/drivers/net/hyperv/rndis_filter.c
index 006c1b8c23857a17757366ffab86fd4eb9bad60b..172824eb219a2f1bc5134525028539655f8817c6 100644 (file)
--- a/drivers/net/hyperv/rndis_filter.c
+++ b/drivers/net/hyperv/rndis_filter.c
@@ -1053,7 +1053,7 @@ int rndis_filter_device_add(struct hv_device *dev,
        ret = rndis_filter_query_device(rndis_device,
                                        RNDIS_OID_GEN_MAXIMUM_FRAME_SIZE,
                                        &mtu, &size);
-       if (ret == 0 && size == sizeof(u32))
+       if (ret == 0 && size == sizeof(u32) && mtu < net_device->ndev->mtu)
                net_device->ndev->mtu = mtu;
 
        /* Get the mac address */