From: Samuel Mendoza-Jonas samjonas@amazon.com
[ Upstream commit fe68195daf34d5dddacd3f93dd3eafc4beca3a0e ]
From 4.17 onwards the ixgbevf driver uses build_skb() to build an skb
around new data in the page buffer shared with the ixgbe PF. This uses either a 2K or 3K buffer, and offsets the DMA mapping by NET_SKB_PAD + NET_IP_ALIGN. When using a smaller buffer RXDCTL is set to ensure the PF does not write a full 2K bytes into the buffer, which is actually 2K minus the offset.
However on the 82599 virtual function, the RXDCTL mechanism is not available. The driver attempts to work around this by using the SET_LPE mailbox method to lower the maximm frame size, but the ixgbe PF driver ignores this in order to keep the PF and all VFs in sync[0].
This means the PF will write up to the full 2K set in SRRCTL, causing it to write NET_SKB_PAD + NET_IP_ALIGN bytes past the end of the buffer. With 4K pages split into two buffers, this means it either writes NET_SKB_PAD + NET_IP_ALIGN bytes past the first buffer (and into the second), or NET_SKB_PAD + NET_IP_ALIGN bytes past the end of the DMA mapping.
Avoid this by only enabling build_skb when using "large" buffers (3K). These are placed in each half of an order-1 page, preventing the PF from writing past the end of the mapping.
[0]: Technically it only ever raises the max frame size, see ixgbe_set_vf_lpe() in ixgbe_sriov.c
Fixes: f15c5ba5b6cd ("ixgbevf: add support for using order 1 pages to receive large frames") Signed-off-by: Samuel Mendoza-Jonas samjonas@amazon.com Tested-by: Konrad Jankowski konrad0.jankowski@intel.com Signed-off-by: Tony Nguyen anthony.l.nguyen@intel.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c index be8e6d4e376ec..9bd02766a4bcc 100644 --- a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c +++ b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c @@ -1979,14 +1979,15 @@ static void ixgbevf_set_rx_buffer_len(struct ixgbevf_adapter *adapter, if (adapter->flags & IXGBEVF_FLAGS_LEGACY_RX) return;
- set_ring_build_skb_enabled(rx_ring); + if (PAGE_SIZE < 8192) + if (max_frame > IXGBEVF_MAX_FRAME_BUILD_SKB) + set_ring_uses_large_buffer(rx_ring);
- if (PAGE_SIZE < 8192) { - if (max_frame <= IXGBEVF_MAX_FRAME_BUILD_SKB) - return; + /* 82599 can't rely on RXDCTL.RLPML to restrict the size of the frame */ + if (adapter->hw.mac.type == ixgbe_mac_82599_vf && !ring_uses_large_buffer(rx_ring)) + return;
- set_ring_uses_large_buffer(rx_ring); - } + set_ring_build_skb_enabled(rx_ring); }
/**