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b2b012afdd
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>
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| 9pfs | ||
| acpi | ||
| adc | ||
| alpha | ||
| arm | ||
| audio | ||
| block | ||
| bt | ||
| char | ||
| core | ||
| cpu | ||
| cris | ||
| display | ||
| dma | ||
| gpio | ||
| i2c | ||
| i386 | ||
| ide | ||
| input | ||
| intc | ||
| ipack | ||
| ipmi | ||
| isa | ||
| lm32 | ||
| m68k | ||
| mem | ||
| microblaze | ||
| mips | ||
| misc | ||
| moxie | ||
| net | ||
| nios2 | ||
| nvram | ||
| openrisc | ||
| pci | ||
| pci-bridge | ||
| pci-host | ||
| pcmcia | ||
| ppc | ||
| s390x | ||
| scsi | ||
| sd | ||
| sh4 | ||
| smbios | ||
| sparc | ||
| sparc64 | ||
| ssi | ||
| timer | ||
| tpm | ||
| tricore | ||
| unicore32 | ||
| usb | ||
| vfio | ||
| virtio | ||
| watchdog | ||
| xen | ||
| xenpv | ||
| xtensa | ||
| Makefile.objs | ||