Re: BUG: sleeping function called from invalid context at mm/slub.c:793

[Avi Kivity <avi@redhat.com>]

On 01/13/2011 02:59 PM, Jan Kiszka wrote:
> >  @@ -5351,6 +5351,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
> >   	int r;
> >   	sigset_t sigsaved;
> >
> >  +	if (!tsk_used_math(current)&&  init_fpu(current))
> >  +		return -ENOMEM;
> >  +
>
> Could become a rainy day for the kvm-kmod maintainer:
>
> For compat support on kernels without init_fpu exported yet, can I
> trigger the same result by simply issuing an FPU instruction here so
> that do_device_not_available will perform the allocation? Not really
> nice, but it doesn't appear to me like there is any code path that would
> complain about in-kernel FPU usage (provided we don't need math
> emulation - which is quite likely).

That's a pessimization, since it forces the fpu to be switched.  If both 
qemu and the guest don't use the fpu, we can run a guest with some other 
task's fpu loaded.

Oh, but if it's after the check for !tsk_used_math(), it only triggers 
once, so that's okay.  I guess something like mov %%xmm0, %%xmm0 should 
do nicely.

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