diff options
author | Andrey Smirnov <andrew.smirnov@gmail.com> | 2018-01-11 13:25:35 +0000 |
---|---|---|
committer | Peter Maydell <peter.maydell@linaro.org> | 2018-01-11 13:25:35 +0000 |
commit | b2b012afdd9c03ba8a1619f45301d34f358d367b (patch) | |
tree | 800e5b6041f4b753a9a867c09daa3b4b6a46027d /hw | |
parent | a6383e99ffc3b615d8465aebbd5d48f1fa9b2949 (diff) | |
download | qemu-b2b012afdd9c03ba8a1619f45301d34f358d367b.zip qemu-b2b012afdd9c03ba8a1619f45301d34f358d367b.tar.gz qemu-b2b012afdd9c03ba8a1619f45301d34f358d367b.tar.bz2 |
imx_fec: Change queue flushing heuristics
In current implementation, packet queue flushing logic seem to suffer
from a deadlock like scenario if a packet is received by the interface
before before Rx ring is initialized by Guest's driver. Consider the
following sequence of events:
1. A QEMU instance is started against a TAP device on Linux
host, running Linux guest, e. g., something to the effect
of:
qemu-system-arm \
-net nic,model=imx.fec,netdev=lan0 \
netdev tap,id=lan0,ifname=tap0,script=no,downscript=no \
... rest of the arguments ...
2. Once QEMU starts, but before guest reaches the point where
FEC deriver is done initializing the HW, Guest, via TAP
interface, receives a number of multicast MDNS packets from
Host (not necessarily true for every OS, but it happens at
least on Fedora 25)
3. Recieving a packet in such a state results in
imx_eth_can_receive() returning '0', which in turn causes
tap_send() to disable corresponding event (tap.c:203)
4. Once Guest's driver reaches the point where it is ready to
recieve packets it prepares Rx ring descriptors and writes
ENET_RDAR_RDAR to ENET_RDAR register to indicate to HW that
more descriptors are ready. And at this points emulation
layer does this:
s->regs[index] = ENET_RDAR_RDAR;
imx_eth_enable_rx(s);
which, combined with:
if (!s->regs[ENET_RDAR]) {
qemu_flush_queued_packets(qemu_get_queue(s->nic));
}
results in Rx queue never being flushed and corresponding
I/O event beign disabled.
To prevent the problem, change the code to always flush packet queue
when ENET_RDAR transitions 0 -> ENET_RDAR_RDAR.
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Philippe Mathieu-Daudé <f4bug@amsat.org>
Cc: qemu-devel@nongnu.org
Cc: qemu-arm@nongnu.org
Cc: yurovsky@gmail.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Diffstat (limited to 'hw')
-rw-r--r-- | hw/net/imx_fec.c | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/hw/net/imx_fec.c b/hw/net/imx_fec.c index 8b2e4b8..eb034ff 100644 --- a/hw/net/imx_fec.c +++ b/hw/net/imx_fec.c @@ -533,7 +533,7 @@ static void imx_eth_do_tx(IMXFECState *s) } } -static void imx_eth_enable_rx(IMXFECState *s) +static void imx_eth_enable_rx(IMXFECState *s, bool flush) { IMXFECBufDesc bd; bool rx_ring_full; @@ -544,7 +544,7 @@ static void imx_eth_enable_rx(IMXFECState *s) if (rx_ring_full) { FEC_PRINTF("RX buffer full\n"); - } else if (!s->regs[ENET_RDAR]) { + } else if (flush) { qemu_flush_queued_packets(qemu_get_queue(s->nic)); } @@ -807,7 +807,7 @@ static void imx_eth_write(void *opaque, hwaddr offset, uint64_t value, if (s->regs[ENET_ECR] & ENET_ECR_ETHEREN) { if (!s->regs[index]) { s->regs[index] = ENET_RDAR_RDAR; - imx_eth_enable_rx(s); + imx_eth_enable_rx(s, true); } } else { s->regs[index] = 0; @@ -930,7 +930,7 @@ static int imx_eth_can_receive(NetClientState *nc) FEC_PRINTF("\n"); - return s->regs[ENET_RDAR] ? 1 : 0; + return !!s->regs[ENET_RDAR]; } static ssize_t imx_fec_receive(NetClientState *nc, const uint8_t *buf, @@ -1020,7 +1020,7 @@ static ssize_t imx_fec_receive(NetClientState *nc, const uint8_t *buf, } } s->rx_descriptor = addr; - imx_eth_enable_rx(s); + imx_eth_enable_rx(s, false); imx_eth_update(s); return len; } @@ -1116,7 +1116,7 @@ static ssize_t imx_enet_receive(NetClientState *nc, const uint8_t *buf, } } s->rx_descriptor = addr; - imx_eth_enable_rx(s); + imx_eth_enable_rx(s, false); imx_eth_update(s); return len; } |