Re: kvm_amd BUG: unable to handle kernel NULL pointer dereference at 00000014

[Avi Kivity <avi@redhat.com>]

On 03/07/2011 03:16 PM, Roedel, Joerg wrote:
> On Mon, Mar 07, 2011 at 07:50:14AM -0500, Avi Kivity wrote:
> >  On 03/07/2011 02:11 PM, Roedel, Joerg wrote:
>
> >  >  There is no access to per_cpu variables at the start of x86_decode_insn.
> >  >  I did a bit of investigation and it turns out that the faulting
> >  >  instruction is inserted into the code by the gcc because the
> >  >  CONFIG_CC_STACKPROTECTOR is enabled.
> >  >  The user tested this is Ubuntu 11.04 alpha-something i386 and this
> >  >  distro uses gcc 4.5.2. So CC_STACKPROTECTOR seems to be harmful with
> >  >  this gcc version but I am not sure whether this counts as a gcc bug.
> >
> >  Ah, looks like %gs is the expected segment on i386 with
> >  -fstack-protector.  So we must disable lazy gs reload in that scenario.
>
> According to the comments in stackprotector.h its the same on amd64 (the
> difference is that gcc expects the canary value at a different offset
> from %gs).
> So we should probably unlazy %gs reload alltogether.

On x86_64 we don't do lazy %gs reload (lazy %fs instead), so it should 
work as is.

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