Since a90a742 "tap: Drop tap_can_send", all nics that returns false from .can_receive() are required to explicitly flush the incoming queue when the status of it is changing back to true, otherwise the backend will sop processing more rx packets.
The purpose of this callback is to tell the peer backend (tap, socket, etc) "hold on until guest consumes old data because my buffer is not ready". More often than not NICs also do this when driver deactivated the card or disabled rx, causing the packets being unnessarily queued, where they should actualy be dropped. This series adds such missing qemu_flush_queued_packets calls for all NICs, and drops such unnecessary conditions in .can_receive(), so that NICs now: - returns false from .can_receive when guest buffers are busy. - calls qemu_flush_queued_packets when buffers are available again. - returns -1 from .receive when rx is not enabled. e1000, ne2000, rocker and vmxnet3 are not included because they're fixed by other patches on the list and applied to Stefan's tree. virtio-net is covered by another thread: https://lists.gnu.org/archive/html/qemu-devel/2015-06/msg07377.html All other NICs are okay, as they already do the flush on the state transition points. Please review. Fam Zheng (12): xgmac: Drop packets with eth_can_rx is false. pcnet: Drop pcnet_can_receive eepro100: Drop nic_can_receive usbnet: Drop usbnet_can_receive etsec: Move etsec_can_receive into etsec_receive etsec: Flush queue when rx buffer is consumed mcf_fec: Drop mcf_fec_can_receive milkymist-minimac2: Flush queued packets when link comes up mipsnet: Flush queued packets when receiving is enabled stellaris_enet: Flush queued packets when read done dp8393x: Flush packets when link comes up axienet: Flush queued packets when rx is done hw/net/dp8393x.c | 8 ++++++++ hw/net/eepro100.c | 11 ----------- hw/net/fsl_etsec/etsec.c | 20 ++++++++++---------- hw/net/fsl_etsec/etsec.h | 4 +++- hw/net/fsl_etsec/rings.c | 15 +++++++++------ hw/net/lance.c | 1 - hw/net/mcf_fec.c | 9 +-------- hw/net/milkymist-minimac2.c | 12 ++++++------ hw/net/mipsnet.c | 9 +++++++-- hw/net/pcnet-pci.c | 1 - hw/net/pcnet.c | 9 --------- hw/net/pcnet.h | 1 - hw/net/stellaris_enet.c | 14 +++++--------- hw/net/xgmac.c | 8 ++++---- hw/net/xilinx_axienet.c | 22 ++++++++++++++++++++++ hw/usb/dev-network.c | 20 ++++---------------- 16 files changed, 79 insertions(+), 85 deletions(-) -- 2.4.3
