CPU Limitations

CPU Limitations

[Cornelius Wefelscheid]

Hi,
i have the following problem:
I got a amd opteron server with 32 (4*8) cpus.

Since kvm is only able to created a virtual machine with 16 cpus, i
changed KVM_MAX_VCPUS, MAX_VCPUS and MAX_CPUS
as suggested in
http://www.linux-kvm.org/wiki/images/b/be/KvmForum2008$kdf2008_6.pdf

after compiling everything is shows the right number of maximum cpus in
the virt-manager,
but it is still not working.

If i start for example my virtual machine with

kvm -m 4000 -smp 30 disk0.img

i get a segmentation fault.
in the logfile it looks like that:

[ 4440.424512] __ratelimit: 18 callbacks suppressed
[ 4440.424523] kvm[7054]: segfault at 1ae5cf6b0 ip 00000000004092ba sp
00007fff3dbb8dc0 error 4 in kvm[400000+1e1000]

Any idee what is missing or what is wrong?

cheers
cornelius

Re: CPU Limitations

[Avi Kivity]

Cornelius Wefelscheid wrote:
> Hi,
> i have the following problem:
> I got a amd opteron server with 32 (4*8) cpus.
>
> Since kvm is only able to created a virtual machine with 16 cpus, i
> changed KVM_MAX_VCPUS, MAX_VCPUS and MAX_CPUS
> as suggested in
> http://www.linux-kvm.org/wiki/images/b/be/KvmForum2008$kdf2008_6.pdf
>
> after compiling everything is shows the right number of maximum cpus in
> the virt-manager,
> but it is still not working.
>
> If i start for example my virtual machine with
>
> kvm -m 4000 -smp 30 disk0.img
>
> i get a segmentation fault.
> in the logfile it looks like that:
>
> [ 4440.424512] __ratelimit: 18 callbacks suppressed
> [ 4440.424523] kvm[7054]: segfault at 1ae5cf6b0 ip 00000000004092ba sp
> 00007fff3dbb8dc0 error 4 in kvm[400000+1e1000]
>
> Any idee what is missing or what is wrong?
>
>   

Get a core dump and look at it with gdb, you'll probably see the problem 
immediately.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

Re: CPU Limitations

[Cornelius Wefelscheid]

Hi,
i tried to get some useful informations out of gdb.
but it just gives me this:

warning: Can't read pathname for load map: Input/output error.
Reading symbols from /lib/libm.so.6...(no debugging symbols
found)...done.
Loaded symbols for /lib/libm.so.6
Reading symbols from /lib/libz.so.1...(no debugging symbols
found)...done.
Loaded symbols for /lib/libz.so.1
Reading symbols from /usr/lib/libasound.so.2...
(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libasound.so.2
Reading symbols from /usr/lib/libpulse-simple.so.0...(no debugging
symbols found)...done.
Loaded symbols for /usr/lib/libpulse-simple.so.0
Reading symbols from /usr/lib/libgnutls.so.26...
(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libgnutls.so.26
Reading symbols from /lib/libpthread.so.0...(no debugging symbols
found)...done.
Loaded symbols for /lib/libpthread.so.0
Reading symbols from /lib/librt.so.1...
(no debugging symbols found)...done.
Loaded symbols for /lib/librt.so.1
Reading symbols from /lib/libutil.so.1...(no debugging symbols
found)...done.
Loaded symbols for /lib/libutil.so.1
Reading symbols from /usr/lib/libX11.so.6...
(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libX11.so.6
Reading symbols from /usr/lib/libSDL-1.2.so.0...(no debugging symbols
found)...done.
Loaded symbols for /usr/lib/libSDL-1.2.so.0
Reading symbols from /lib/libncurses.so.5...
(no debugging symbols found)...done.
Loaded symbols for /lib/libncurses.so.5
Reading symbols from /lib/libc.so.6...(no debugging symbols
found)...done.
Loaded symbols for /lib/libc.so.6
Reading symbols from /usr/lib/libpulse.so.0...
(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libpulse.so.0
Reading symbols from /lib/libdl.so.2...(no debugging symbols
found)...done.
Loaded symbols for /lib/libdl.so.2
Reading symbols from /usr/lib/libSM.so.6...
(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libSM.so.6
Reading symbols from /usr/lib/libICE.so.6...(no debugging symbols
found)...done.
Loaded symbols for /usr/lib/libICE.so.6
Reading symbols from /lib/libcap.so.2...
(no debugging symbols found)...done.
Loaded symbols for /lib/libcap.so.2
Reading symbols from /usr/lib/libgdbm.so.3...(no debugging symbols
found)...done.
Loaded symbols for /usr/lib/libgdbm.so.3
Reading symbols from /usr/lib/libtasn1.so.3...
(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libtasn1.so.3
Reading symbols from /lib/libgcrypt.so.11...(no debugging symbols
found)...done.
Loaded symbols for /lib/libgcrypt.so.11
Reading symbols from /lib/ld-linux-x86-64.so.2...
(no debugging symbols found)...done.
Loaded symbols for /lib64/ld-linux-x86-64.so.2
Reading symbols from /usr/lib/libxcb.so.1...(no debugging symbols
found)...done.
Loaded symbols for /usr/lib/libxcb.so.1
Reading symbols from /usr/lib/libdirectfb-1.0.so.0...
(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libdirectfb-1.0.so.0
Reading symbols from /usr/lib/libfusion-1.0.so.0...(no debugging symbols
found)...done.
Loaded symbols for /usr/lib/libfusion-1.0.so.0
Reading symbols from /usr/lib/libdirect-1.0.so.0...
(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libdirect-1.0.so.0
Reading symbols from /lib/libuuid.so.1...(no debugging symbols
found)...done.
Loaded symbols for /lib/libuuid.so.1
Reading symbols from /lib/libattr.so.1...
(no debugging symbols found)...done.
Loaded symbols for /lib/libattr.so.1
Reading symbols from /lib/libgpg-error.so.0...(no debugging symbols
found)...done.
Loaded symbols for /lib/libgpg-error.so.0
Reading symbols from /usr/lib/libXau.so.6...
(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libXau.so.6
Reading symbols from /usr/lib/libXdmcp.so.6...(no debugging symbols
found)...done.
Loaded symbols for /usr/lib/libXdmcp.so.6
Reading symbols from /lib/libnss_files.so.2...
---Type <return> to continue, or q <return> to quit---
(no debugging symbols found)...done.
Loaded symbols for /lib/libnss_files.so.2
(no debugging symbols found)
Core was generated by `kvm -smp 32 /fs2/xen/disk0'.
Program terminated with signal 11, Segmentation fault.
[New process 4665]
[New process 4666]
[New process 4674]
[New process 4670]
[New process 4676]
[New process 4678]
[New process 4669]
[New process 4667]
[New process 4677]
[New process 4686]
[New process 4675]
[New process 4672]
[New process 4679]
[New process 4682]
[New process 4673]
[New process 4681]
[New process 4671]
[New process 4683]
[New process 4689]
[New process 4685]
[New process 4668]
[New process 4690]
[New process 4684]
[New process 4691]
[New process 4687]
[New process 4692]
[New process 4693]
[New process 4694]
[New process 4695]
[New process 4696]
[New process 4680]
[New process 4688]
[New process 4697]
#0  0x00000000004092ba in ?? ()



Do i maybe need to compile KVM with some special debug flags?
Is there no patch that increases the number of CPUS?

Cheers,
Cornelius



Am Dienstag, den 28.04.2009, 11:41 +0300 schrieb Avi Kivity:
> Cornelius Wefelscheid wrote:
> > Hi,
> > i have the following problem:
> > I got a amd opteron server with 32 (4*8) cpus.
> >
> > Since kvm is only able to created a virtual machine with 16 cpus, i
> > changed KVM_MAX_VCPUS, MAX_VCPUS and MAX_CPUS
> > as suggested in
> > http://www.linux-kvm.org/wiki/images/b/be/KvmForum2008$kdf2008_6.pdf
> >
> > after compiling everything is shows the right number of maximum cpus in
> > the virt-manager,
> > but it is still not working.
> >
> > If i start for example my virtual machine with
> >
> > kvm -m 4000 -smp 30 disk0.img
> >
> > i get a segmentation fault.
> > in the logfile it looks like that:
> >
> > [ 4440.424512] __ratelimit: 18 callbacks suppressed
> > [ 4440.424523] kvm[7054]: segfault at 1ae5cf6b0 ip 00000000004092ba sp
> > 00007fff3dbb8dc0 error 4 in kvm[400000+1e1000]
> >
> > Any idee what is missing or what is wrong?
> >
> >   
> 
> Get a core dump and look at it with gdb, you'll probably see the problem 
> immediately.
> 

Re: CPU Limitations

[Avi Kivity]

Cornelius Wefelscheid wrote:
> Hi,
> i tried to get some useful informations out of gdb.
> but it just gives me this:
>
> #0  0x00000000004092ba in ?? ()
>
>
>
> Do i maybe need to compile KVM with some special debug flags?
> Is there no patch that increases the number of CPUS?
>   

Use 'gdb /path/to/qemu core_file'


-- 
error compiling committee.c: too many arguments to function