[Qemu-devel] [Bug 1073952] [NEW] data sent to serial interface gets truncated after 64kb

[David Jaschuk]

Public bug reported:

When sending more than 64kb of data to the serial interface in a short
timespan, the data seems to disappear.

I tested it with the latest release (qemu-kvm-1.2.0-rc2.tar.gz) where
the bug still occurs. I stumbled upon it when I upraged my qemu version.
The bug did not occur in the last version i had (0.12.5).

You can reproduce it as follows:

1. Start a dd or cat command in one terminal and pipe the output to a
netcat. The testfile has to be larger than 64kb. I used one that had
93kb and did contain only ascii text.

     $ dd if=<TESTFILE> | nc -l 127.0.0.1 65432
     or
     $ cat <TESTFILE> | nc -l 127.0.0.1 65432

2. Start a qemu and let the first serial port connect to the listening
netcat. I suppose that the testsystem can be any system that does not
read from the serial port on its own (e.g. during boot process). I used
a self compiled minimal linux.

     $ qemu -cdrom <TESTSYSTEM> -serial tcp:127.0.0.1:65432

3. When the testsystem is booted, read from the serial device and write
it to a file.

     $ dd if=/dev/ttyS0 of=/tmp/testFile
     or
     $ cat /dev/ttyS0 > /tmp/testFile


The result in almost all of my testruns is, that the /tmp/testFile does only 
has the size of 64kb. The rest of the data vanished. In some cases the file was 
slightly bigger (65kb or 67kb) but allways under 70kb. The complete file (93kb) 
was not trasmitted in any of the runs.

I hope my explanation is exactly enough for you to reproduce it.

** Affects: qemu
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1073952

Title:
  data sent to serial interface gets truncated after 64kb

Status in QEMU:
  New

Bug description:
  When sending more than 64kb of data to the serial interface in a short
  timespan, the data seems to disappear.

  I tested it with the latest release (qemu-kvm-1.2.0-rc2.tar.gz) where
  the bug still occurs. I stumbled upon it when I upraged my qemu
  version. The bug did not occur in the last version i had (0.12.5).

  You can reproduce it as follows:

  1. Start a dd or cat command in one terminal and pipe the output to a
  netcat. The testfile has to be larger than 64kb. I used one that had
  93kb and did contain only ascii text.

       $ dd if=<TESTFILE> | nc -l 127.0.0.1 65432
       or
       $ cat <TESTFILE> | nc -l 127.0.0.1 65432

  2. Start a qemu and let the first serial port connect to the listening
  netcat. I suppose that the testsystem can be any system that does not
  read from the serial port on its own (e.g. during boot process). I
  used a self compiled minimal linux.

       $ qemu -cdrom <TESTSYSTEM> -serial tcp:127.0.0.1:65432

  3. When the testsystem is booted, read from the serial device and
  write it to a file.

       $ dd if=/dev/ttyS0 of=/tmp/testFile
       or
       $ cat /dev/ttyS0 > /tmp/testFile

  
  The result in almost all of my testruns is, that the /tmp/testFile does only 
has the size of 64kb. The rest of the data vanished. In some cases the file was 
slightly bigger (65kb or 67kb) but allways under 70kb. The complete file (93kb) 
was not trasmitted in any of the runs.

  I hope my explanation is exactly enough for you to reproduce it.

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