On 04/20/2015 08:07 PM, David Gibson wrote: > AFAIK the PAPR document which defines the virtual device interface used by > the ibmveth driver doesn't specify a specific maximum MTU. So, in the > ibmveth driver, the maximum allowed MTU is determined by the maximum > allocated buffer size of 64k (corresponding to one page in the common case) > minus the per-buffer overhead IBMVETH_BUFF_OH (which has value 22 for 14 > bytes of ethernet header, plus 8 bytes for an opaque handle). > > This suggests a maximum allowable MTU of 65514 bytes, but in fact the > driver only permits a maximum MTU of 65513. This is because there is a < > instead of an <= in ibmveth_change_mtu(), which only permits an MTU which > is strictly smaller than the buffer size, rather than allowing the buffer > to be completely filled. > > This patch fixes the buglet.
Thanks! Acked-by: Thomas Falcon <tlfal...@linux.vnet.ibm.com> > > Signed-off-by: David Gibson <da...@gibson.dropbear.id.au>1 > --- > drivers/net/ethernet/ibm/ibmveth.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > Changes since v1: > * Fixed a second instance of the same off-by-one error. Thanks to > Thomas Falcon for spotting this. > > diff --git a/drivers/net/ethernet/ibm/ibmveth.c > b/drivers/net/ethernet/ibm/ibmveth.c > index cd7675a..1813476 100644 > --- a/drivers/net/ethernet/ibm/ibmveth.c > +++ b/drivers/net/ethernet/ibm/ibmveth.c > @@ -1238,7 +1238,7 @@ static int ibmveth_change_mtu(struct net_device *dev, > int new_mtu) > return -EINVAL; > > for (i = 0; i < IBMVETH_NUM_BUFF_POOLS; i++) > - if (new_mtu_oh < adapter->rx_buff_pool[i].buff_size) > + if (new_mtu_oh <= adapter->rx_buff_pool[i].buff_size) > break; > > if (i == IBMVETH_NUM_BUFF_POOLS) > @@ -1257,7 +1257,7 @@ static int ibmveth_change_mtu(struct net_device *dev, > int new_mtu) > for (i = 0; i < IBMVETH_NUM_BUFF_POOLS; i++) { > adapter->rx_buff_pool[i].active = 1; > > - if (new_mtu_oh < adapter->rx_buff_pool[i].buff_size) { > + if (new_mtu_oh <= adapter->rx_buff_pool[i].buff_size) { > dev->mtu = new_mtu; > vio_cmo_set_dev_desired(viodev, > ibmveth_get_desired_dma _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev