From 5e88240cfd4e6b1b08d6bef64854fb435ece1e52 Mon Sep 17 00:00:00 2001 From: Samuel Mendoza-Jonas Date: Thu, 3 Feb 2022 14:49:16 -0800 Subject: [PATCH] ixgbevf: Require large buffers for build_skb on 82599VF 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: 85c3b97d1e7c ("ixgbevf: add support for using order 1 pages to receive large frames") Signed-off-by: Samuel Mendoza-Jonas Tested-by: Konrad Jankowski Signed-off-by: Tony Nguyen Signed-off-by: David S. Miller --- 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 0015fcf1df2b0..0f293acd17e89 100644 --- a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c +++ b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c @@ -1984,14 +1984,15 @@ 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); } /** -- 2.39.5