powerpc/vas: do not set uses_vas for kernel windows

[Michael Ellerman]

On Thu, 2018-02-08 at 09:18:38 UTC, Nicholas Piggin wrote:
> cp_abort is only required or user windows, because kernel context
> must not be preempted between a copy/paste pair.
> 
> Without this patch, the init task gets used_vas set when it runs
> the nx842_powernv_init initcall, which opens windows for kernel
> usage.
> 
> used_vas is then never cleared anywhere, so it gets propagated
> into all other tasks. It's a property of the address space, so it
> should really be cleared when a new mm is created (or in dup_mmap
> if the mmaps are marked as VM_DONTCOPY). For now we seem to have
> no such driver, so leave that for another patch.
> 
> Cc: Sukadev Bhattiprolu <sukadev at linux.vnet.ibm.com>
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
> Reviewed-by: Sukadev Bhattiprolu <sukadev at linux.vnet.ibm.com>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/b00b62898631b756c3e123542bbb04

cheers