Re: KVM 29: Page fault in kernel mode while booting GNU/kFreeBSD

[Aurelien Jarno <aurelien-rXXEIb44qovR7s880joybQ@public.gmane.org>]

On Sun, Jul 15, 2007 at 03:30:43PM +0300, Avi Kivity wrote:
> Aurelien Jarno wrote:
> >On Sun, Jul 15, 2007 at 09:23:31AM +0300, Avi Kivity wrote:
> >  
> >>Can you bisect kvm to find the offending commit?  Basically, you do a
> >>
> >>  git clone git://git.kernel.org/pub/scm/linux/kernel/git/avi/kvm.git
> >>  cd kvm
> >>  git bisect start drivers/kvm/
> >>  bit bisect bad kvm-29
> >>  git bisect good kvm-28
> >>
> >>git will check out a test candidate; go to your kvm userspace directory 
> >>and do
> >>
> >>  make -C kernel sync LINUX=/path/to/the/kvm/git/directory
> >>  make -C kernel
> >>  sudo make -C kernel install
> >>
> >>reload the module, test, and issue 'git bisect good' or 'git bisect bad' 
> >>according to the result.  As there are only 25 commits you should be 
> >>done in 5 cycles.
> >>
> >>    
> >
> >And the result is:
> >
> >commit ba9c20c048726037664d303362b688759fdf6e9d
> >Author: Luca Tettamanti <kronos.it-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> >Date:   Tue Jun 19 22:41:20 2007 +0200
> >
> >    KVM: Fix x86 emulator writeback
> >    
> >    When the old value and new one are the same the emulator skips the
> >    write; this is undesirable when the destination is a MMIO area and the
> >    write shall be performed regardless of the previous value. This
> >    optimization breaks e.g. a Linux guest APIC compiled without
> >    X86_GOOD_APIC.
> >    
> >    Remove the check and perform the writeback stage in the emulation 
> >    unless
> >    it's explicitly disabled (currently push and some 2 bytes instructions
> >    may disable the writeback).
> >    
> >    Signed-Off-By: Luca Tettamanti <kronos.it-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> >    Signed-off-by: Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
> >
> >
> >I have tried to revert this patch directly into kvm-29, and it also
> >fixes the problem.
> >
> >  
> 
> From a cursory inspection, looks like the cmov instructions were broken 
> by the patch.  Can you try the attached patch on top of kvm-29?
> 

Unfortunately this does not fix the problem.

-- 
  .''`.  Aurelien Jarno	            | GPG: 1024D/F1BCDB73
 : :' :  Debian developer           | Electrical Engineer
 `. `'   aurel32-8fiUuRrzOP0dnm+yROfE0A@public.gmane.org         | aurelien-rXXEIb44qovR7s880joybQ@public.gmane.org
   `-    people.debian.org/~aurel32 | www.aurel32.net

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