From fee9d348ffc5c9f80068086799a948996f633f7e Mon Sep 17 00:00:00 2001 From: Fernando Luis Vazquez Cao Date: Mon, 4 Jun 2012 17:35:11 +0300 Subject: rtl8139: honor RxOverflow flag in can_receive method Some drivers (Linux' 8139too among them) rely on the NIC injecting an interrupt in the event of a receive buffer overflow and, accordingly, set the RxOverflow bit in the interrupt mask. Unfortunately rtl8139's can_receive method ignores the RxOverflow flag, which may lead to a situation where rtl8139 stops receiving packets (can_receive returns 0) when the receive buffer becomes full. If the driver eventually read from the receive buffer or reset the card the emulator could recover from this situation. However some implementations only do this upon receiving an interrupt with either RxOK or RxOverflow set in the ISR; interrupt that will never come because QEMU's flow control mechanisms would prevent rtl8139 from receiving any packet. Letting packets go through when the overflow interrupt is enabled makes the QEMU emulator compliant to the spec and solves the problem. This patch should fix a relatively common (in our experience) network stall observed when running enterprise distros with rtl8139 as the NIC; in some cases the 8139too device driver gets loaded and when under heavy load the network eventually stops working. Reported-by: Hayato Kakuta Tested-by: Hayato Kakuta Acked-by: Igor Kovalenko Signed-off-by: Fernando Luis Vazquez Cao Signed-off-by: Michael S. Tsirkin --- hw/rtl8139.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/hw/rtl8139.c b/hw/rtl8139.c index 2413bc3d25..060404c137 100644 --- a/hw/rtl8139.c +++ b/hw/rtl8139.c @@ -799,7 +799,7 @@ static int rtl8139_can_receive(VLANClientState *nc) } else { avail = MOD2(s->RxBufferSize + s->RxBufPtr - s->RxBufAddr, s->RxBufferSize); - return (avail == 0 || avail >= 1514); + return (avail == 0 || avail >= 1514 || (s->IntrMask & RxOverflow)); } } -- cgit v1.2.3