* [Qemu-devel] How to capture guest %rip from a qemu process without monitor?
@ 2011-09-30 7:42 Richard W.M. Jones
2011-09-30 8:49 ` Jan Kiszka
0 siblings, 1 reply; 3+ messages in thread
From: Richard W.M. Jones @ 2011-09-30 7:42 UTC (permalink / raw)
To: qemu-devel
I've finally managed to reproduce a very infrequent kernel boot hang
by forcing TCG (so it runs slower, bug seems to be timing sensitive)
and running a boot test in a loop thousands of times.
I'd like to find out where in the guest kernel this is looping.
Unfortunately I don't have access to the monitor so "info registers"
won't work, but I can attach to the qemu process with gdb.
Which TCG struct contains %rip, other registers? What other useful
information can be captured using only gdb?
Rich.
https://bugzilla.redhat.com/show_bug.cgi?id=723822
Command line:
qemu-kvm -machine pc,accel=tcg -drive file=/dev/null,if=virtio
-nodefconfig -nodefaults -nographic -m 500 -no-reboot -no-hpet -device
virtio-serial -serial stdio -chardev
socket,path=/home/rjones/d/libguestfs/libguestfsoFRvo0/guestfsd.sock,id=channel0
-device virtserialport,chardev=channel0,name=org.libguestfs.channel.0
-kernel /home/rjones/d/libguestfs/.guestfs-500/kernel.27140 -initrd
/home/rjones/d/libguestfs/.guestfs-500/initrd.27140 -append 'panic=1
console=ttyS0 udevtimeout=300 no_timer_check acpi=off printk.time=1
cgroup_disable=memory selinux=0 guestfs_verbose=1 TERM=xterm' -drive
file=/home/rjones/d/libguestfs/.guestfs-500/root.27140,snapshot=on,if=virtio,cache=unsafe
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
New in Fedora 11: Fedora Windows cross-compiler. Compile Windows
programs, test, and build Windows installers. Over 70 libraries supprt'd
http://fedoraproject.org/wiki/MinGW http://www.annexia.org/fedora_mingw
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Qemu-devel] How to capture guest %rip from a qemu process without monitor?
2011-09-30 7:42 [Qemu-devel] How to capture guest %rip from a qemu process without monitor? Richard W.M. Jones
@ 2011-09-30 8:49 ` Jan Kiszka
2011-09-30 9:03 ` Richard W.M. Jones
0 siblings, 1 reply; 3+ messages in thread
From: Jan Kiszka @ 2011-09-30 8:49 UTC (permalink / raw)
To: Richard W.M. Jones; +Cc: qemu-devel
On 2011-09-30 09:42, Richard W.M. Jones wrote:
>
> I've finally managed to reproduce a very infrequent kernel boot hang
> by forcing TCG (so it runs slower, bug seems to be timing sensitive)
> and running a boot test in a loop thousands of times.
>
> I'd like to find out where in the guest kernel this is looping.
>
> Unfortunately I don't have access to the monitor so "info registers"
> won't work, but I can attach to the qemu process with gdb.
>
> Which TCG struct contains %rip, other registers? What other useful
> information can be captured using only gdb?
Print first_cpu->eip, maybe also first_cpu->segs[1] to dump the CS
segment cache (relevant while in real mode).
Jan
--
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Qemu-devel] How to capture guest %rip from a qemu process without monitor?
2011-09-30 8:49 ` Jan Kiszka
@ 2011-09-30 9:03 ` Richard W.M. Jones
0 siblings, 0 replies; 3+ messages in thread
From: Richard W.M. Jones @ 2011-09-30 9:03 UTC (permalink / raw)
To: Jan Kiszka; +Cc: qemu-devel
On Fri, Sep 30, 2011 at 10:49:20AM +0200, Jan Kiszka wrote:
> On 2011-09-30 09:42, Richard W.M. Jones wrote:
> >
> > I've finally managed to reproduce a very infrequent kernel boot hang
> > by forcing TCG (so it runs slower, bug seems to be timing sensitive)
> > and running a boot test in a loop thousands of times.
> >
> > I'd like to find out where in the guest kernel this is looping.
> >
> > Unfortunately I don't have access to the monitor so "info registers"
> > won't work, but I can attach to the qemu process with gdb.
> >
> > Which TCG struct contains %rip, other registers? What other useful
> > information can be captured using only gdb?
>
> Print first_cpu->eip, maybe also first_cpu->segs[1] to dump the CS
> segment cache (relevant while in real mode).
Perfect thanks!
*first_cpu contains a wealth of info.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
New in Fedora 11: Fedora Windows cross-compiler. Compile Windows
programs, test, and build Windows installers. Over 70 libraries supprt'd
http://fedoraproject.org/wiki/MinGW http://www.annexia.org/fedora_mingw
^ permalink raw reply [flat|nested] 3+ messages in thread
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2011-09-30 7:42 [Qemu-devel] How to capture guest %rip from a qemu process without monitor? Richard W.M. Jones
2011-09-30 8:49 ` Jan Kiszka
2011-09-30 9:03 ` Richard W.M. Jones
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