kvm problems with Intel host and netbsd/linux guests

kvm problems with Intel host and netbsd/linux guests

[Jim Paris]

Hi,

I'm having trouble getting kvm to work on my system.
The host has 2 dual-core Intel Xeon 5130 CPUs (flags: lm vmx)
and is running Linux 2.6.20.1 with kvm-15 (although I've had no luck
with kvm-12 or kvm-14 either)

If I take (for example) the NetBSD amd64 installation:

  ftp://ftp.netbsd.org/pub/NetBSD/NetBSD-3.1/amd64/installation/cdrom/amd64cd-3.1.iso

and run it with

  qemu-img create hda.img 4G
  qemu-system-x86_64 -cdrom amd64cd-3.1.iso -hda hda.img -boot d

then the screen flashes briefly but qemu crashes with

  unhandled vm exit:  0x80000021
  rax 0000000000000000 rbx 0000000000000000 rcx 0000000000000000 rdx 0000000000000600
  rsi 0000000000000000 rdi 0000000000000000 rsp 0000000000000000 rbp 0000000000000000
  r8  0000000000000000 r9  0000000000000000 r10 0000000000000000 r11 0000000000000000
  r12 0000000000000000 r13 0000000000000000 r14 0000000000000000 r15 0000000000000000
  rip 000000000000fff0 rflags 00023002
  cs f000 (ffff0000/0000ffff p 1 dpl 3 db 0 s 1 type 3 l 0 g 0 avl 0)
  ds 0000 (00000000/0000ffff p 1 dpl 3 db 0 s 1 type 3 l 0 g 0 avl 0)
  es 0000 (00000000/0000ffff p 1 dpl 3 db 0 s 1 type 3 l 0 g 0 avl 0)
  ss 0000 (00000000/0000ffff p 1 dpl 3 db 0 s 1 type 3 l 0 g 0 avl 0)
  fs 0000 (00000000/0000ffff p 1 dpl 3 db 0 s 1 type 3 l 0 g 0 avl 0)
  gs 0000 (00000000/0000ffff p 1 dpl 3 db 0 s 1 type 3 l 0 g 0 avl 0)
  tr 0000 (08850000/00002088 p 1 dpl 0 db 0 s 0 type b l 0 g 0 avl 0)
  ldt 0000 (00000000/0000ffff p 1 dpl 0 db 0 s 0 type 0 l 0 g 0 avl 0)
  gdt 0/ffff
  idt 0/ffff
  cr0 60000010 cr2 0 cr3 0 cr4 0 cr8 0 efer 0
  Aborted

If I try to run it without kvm:

  qemu-system-x86_64 -no-kvm -cdrom amd64cd-3.1.iso -hda hda.img -boot d

Then I get a blank SDL window that is entirely frozen (can't even
switch to the qemu monitor).  If I use a stock qemu 0.8.2 to boot the
cdrom and run the installer, then try to boot the resulting disk image
with kvm:

  qemu-system-x86_64 -hda hda.img -boot c
  qemu-system-x86_64 -no-kvm -hda hda.img -boot c

then I get the exact same results -- the first crashes with "unhandled
vm exit" and the second freezes.

Any suggestions?

Also, on the Linux side of things, I have a disk image from a computer
that also crashes when I try to boot it.  It dies with "exception 14"
after Grub.  But, it does work fine with -no-kvm.  The kernel it's
booting is a 32-bit k7 optimized kernel; is it expected behavior for
that to work fine under -no-kvm but crash on an Intel host?

-jim

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Re: kvm problems with Intel host and netbsd/linux guests

[Avi Kivity]

Jim Paris wrote:
> Hi,
>
> I'm having trouble getting kvm to work on my system.
> The host has 2 dual-core Intel Xeon 5130 CPUs (flags: lm vmx)
> and is running Linux 2.6.20.1 with kvm-15 (although I've had no luck
> with kvm-12 or kvm-14 either)
>
> If I take (for example) the NetBSD amd64 installation:
>
>   ftp://ftp.netbsd.org/pub/NetBSD/NetBSD-3.1/amd64/installation/cdrom/amd64cd-3.1.iso
>
> and run it with
>
>   qemu-img create hda.img 4G
>   qemu-system-x86_64 -cdrom amd64cd-3.1.iso -hda hda.img -boot d
>
> then the screen flashes briefly but qemu crashes with
>
>   unhandled vm exit:  0x80000021
>   rax 0000000000000000 rbx 0000000000000000 rcx 0000000000000000 rdx 0000000000000600
>   rsi 0000000000000000 rdi 0000000000000000 rsp 0000000000000000 rbp 0000000000000000
>   r8  0000000000000000 r9  0000000000000000 r10 0000000000000000 r11 0000000000000000
>   r12 0000000000000000 r13 0000000000000000 r14 0000000000000000 r15 0000000000000000
>   rip 000000000000fff0 rflags 00023002
>   cs f000 (ffff0000/0000ffff p 1 dpl 3 db 0 s 1 type 3 l 0 g 0 avl 0)
>   ds 0000 (00000000/0000ffff p 1 dpl 3 db 0 s 1 type 3 l 0 g 0 avl 0)
>   es 0000 (00000000/0000ffff p 1 dpl 3 db 0 s 1 type 3 l 0 g 0 avl 0)
>   ss 0000 (00000000/0000ffff p 1 dpl 3 db 0 s 1 type 3 l 0 g 0 avl 0)
>   fs 0000 (00000000/0000ffff p 1 dpl 3 db 0 s 1 type 3 l 0 g 0 avl 0)
>   gs 0000 (00000000/0000ffff p 1 dpl 3 db 0 s 1 type 3 l 0 g 0 avl 0)
>   tr 0000 (08850000/00002088 p 1 dpl 0 db 0 s 0 type b l 0 g 0 avl 0)
>   ldt 0000 (00000000/0000ffff p 1 dpl 0 db 0 s 0 type 0 l 0 g 0 avl 0)
>   gdt 0/ffff
>   idt 0/ffff
>   cr0 60000010 cr2 0 cr3 0 cr4 0 cr8 0 efer 0
>   Aborted
>
>   

It looks like the guest is rebooting (rip = 0xfff0), probably due to an 
earlier bug, so the register dump doesn't tell us much.


> If I try to run it without kvm:
>
>   qemu-system-x86_64 -no-kvm -cdrom amd64cd-3.1.iso -hda hda.img -boot d
>
> Then I get a blank SDL window that is entirely frozen (can't even
> switch to the qemu monitor).  If I use a stock qemu 0.8.2 to boot the
> cdrom and run the installer, then try to boot the resulting disk image
> with kvm:
>
>   qemu-system-x86_64 -hda hda.img -boot c
>   qemu-system-x86_64 -no-kvm -hda hda.img -boot c
>
> then I get the exact same results -- the first crashes with "unhandled
> vm exit" and the second freezes.
>
> Any suggestions?
>
> Also, on the Linux side of things, I have a disk image from a computer
> that also crashes when I try to boot it.  It dies with "exception 14"
> after Grub.  But, it does work fine with -no-kvm.  The kernel it's
> booting is a 32-bit k7 optimized kernel; is it expected behavior for
> that to work fine under -no-kvm but crash on an Intel host?
>   

If the kernel uses AMD-specific instructions, yes.  Can you send .config 
for that kernel?

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


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Re: kvm problems with Intel host and netbsd/linux guests

[Jim Paris]

Avi Kivity wrote:

> >Also, on the Linux side of things, I have a disk image from a computer
> >that also crashes when I try to boot it.  It dies with "exception 14"
> >after Grub.  But, it does work fine with -no-kvm.  The kernel it's
> >booting is a 32-bit k7 optimized kernel; is it expected behavior for
> >that to work fine under -no-kvm but crash on an Intel host?
> >  
> 
> If the kernel uses AMD-specific instructions, yes.  Can you send .config 
> for that kernel?

I think it's the stock debian 2.6.18-1-k7 kernel, not sure as it's a
disk image from someone else's machine.  The config has
  CONFIG_X86_32=y
  CONFIG_MK7=y
http://jim.sh/~jim/tmp/config-2.6.18-1-k7

I've managed to get it to boot with KVM by booting first with -no-kvm
and installing the 2.6.18-1-686 kernel.  And that seems to mostly
work, except that I get occasional random segfaults inside the guest
OS.  I also get the same thing when booting e.g. a FreeBSD liveCD
(FreeSBIE).  Sigh.  Not sure how to easily reproduce or debug that.

-jim


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