On 04/22/2015 02:42 PM, Thomas Falcon wrote: > 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
PAPR itself doesn't, but the max-frame-size property, which I understand to be synonymous with max MTU, is required by PAPR to be present in the Logical LAN OF node corresponding to the ibmveth device. -Tyrel >> 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 > _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev