RE: [Xen-users] Issues running WinXP using hvmloader

[Mark Cave-Ayland <mark.cave-ayland@xxxxxxxxxxxx>]

Hi Mats,

Thanks for your help so far with this. I took the plunge yesterday of
using Mercurial to download the latest xen-3.0.3-testing.hg repository
from http://xenbits.xensource.com/ and it looks as if things have
definitely improved:

- WinXP doms now shutdown cleanly without leaving zombies
- My PC no longer crashes when I do a "shutdown -h now"

I still can't start up a WinXP dom with "vcpus = 2" in the configuration
file at the moment; rather than crashing the dom like 3.0.2 did,
3.0.3-testing switches back to 1 CPU before loading. Trying to alter the
vcpus using "xm vcpu-set" doesn't change the vcpu value either.

The only other issue is that I still can't debug a program using MingW's
gdb under a WinXP running in a Xen dom, which I think may be related to
something in the WinXP debug API, or the way that Xen handles segfaults.
Here is the test program that I am using under MingW/msys:


#include <stdlib.h>

int main()
{
char buffer[2];

printf("Hello World!");

strcpy(buffer, "This is a very long string designed to do bad things");
}


If I run this under a Xen WinXP dom then WinXP crashes as expected,
throwing up the normal MS crash dialog. Normally closing the crash
dialog results in termination of the program that produced it. Under Xen
I find I have to manually terminate the crashed program by using Task
Manager or invoking Ctrl-C from the console that launched it!

The other issue is that gdb still can't attach to a program to debug it;
attempting to attach gdb to any process results in a SIGTRAP in part of
the debugging API and it is impossible to get past this point. The
function where the SIGTRAP occurs is always the same, "ntdll!
DbgUiConnectToDbg", no matter which process you try and attach to. This
makes me think that something in this function is raising an exception
which is being incorrectly handled.


$ gdb -p 500
GNU gdb 6.3
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you
are
welcome to change it and/or distribute copies of it under certain
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for
details.
This GDB was configured as "i686-pc-mingw32".
Attaching to process 500
error reading the process's file name: 5
[Switching to thread 500.0x2e4]
(gdb) bt
#0  0x7c901230 in ntdll!DbgUiConnectToDbg () from C:\WINDOWS\system32
\ntdll.dll
#1  0x7c9507a8 in ntdll!KiIntSystemCall () from C:\WINDOWS\system32
\ntdll.dll
#2  0x00000005 in ?? ()
#3  0x00000004 in ?? ()
#4  0x00000001 in ?? ()

...etc...


Any other thoughts?


Kind regards,

Mark.




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