Re: [Xen-users] Is Xen and Qemu serial driver code related ?

[Aleš Rom <ales.rom@xxxxxxxxxxxx>]

Petersson, Mats pravi:
>  
>
>   
> > -----Original Message-----
> > From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> > [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Aleš Rom
> > Sent: 08 February 2007 12:55
> > To: xen-users@xxxxxxxxxxxxxxxxxxx
> > Subject: [Xen-users] Is Xen and Qemu serial driver code related ?
> >
> > Hi.
> >
> > A noticed a very strange thing. A few weeks ago I installed WindowsXP 
> > under qemu. I have serial device attached to COM1 port and 
> > comunication 
> > works.
> > Basicaly I have to download a few hundred bytes from that 
> > serial device 
> > to computer. Every time comunication stops at 83% (5/6).
> > The weird thing is, that when I use Xen, I can see exactly 
> > same thing. 
> > Stops at 83%. Is this related or just coincidence? Is it my 
> > hardware?  
> > Windows on "real" hardware doesn't have this problem.
> >     
> Sounds like it could be the same problem - Xen in HVM mode uses QEMU (a slightly modified source that builds the binary called qemu-dm, which lives in /usr/lib{64}/xen/bin or some such) to emulate the hardware in the guest. Serial port(s) is part of this emulated hardware. 
>
> However, it could be "just about anything". If it's caused by the software, it would probably help to "log" the serial comms 
> somehow (I've successfully written code to take two serial ports on a machine and "copy" the data from one port to the other, making it a 
> "logging station", but there may be other ways to do it, for example let qemu dump the serial port data onto a file - probably requires a 
> little bit of hacking in qemu, but not terribly hard work, if you know a bit about programming). A good place to start this would be in 
> ".../tools/ioemu/hw/serial.c" - the functons serial_ioport_write() and serial_ioport_read(), particularly "addr 0", which is the 
> "data" address. Here's what I would add:
> New variable around the beginning of serial.c (after the #include statements):
> FILE *serial_log;
> In serial_init() add:
>    serial_log = fopen("/tmp/serial.log", "w");
>    if (serial_log == NULL) { 
> 	fprintf(logfile, "Failed to open /tmp/serial.log");
> 	exit(1); 
>    }
> In serial_ioport_write():
> At "case 0", just before the "break" add:
>    fprintf(serial_log, "TX: %02x\n", val);
>
> In serial_ioport_read():
> At "case 0", just before the "break" add:
>    fprintf(serial_log, "RX: %02x\n", ret);
>
> --
> Mats
>   
Thanks Mats. I added these few lines in qemu source (xen was too much 
for me - sorry), rebuild and serial.log produced by qemu is here: 
http://www.p-rom.si/serial.log
The last few lines before data download stops are:

...
...
RX: 6f
RX: 6e
RX: 36
RX: 20
RX: 20
RX: 20
RX: 20
RX:

It looks that the communication stops because there is no data from 
serial device?
Aleš


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