powerpc: Fix possible unrecoverable exception caused by '70fe3d9'

[Michael Ellerman]

On Wed, 2016-16-03 at 02:29:30 UTC, Cyril Bur wrote:
> Commit 70fe3d9 "powerpc: Restore FPU/VEC/VSX if previously used" introduces a
> call to restore_math() late in the syscall return path, after MSR_RI has been
> cleared. The MSR_RI flag is used to indicate whether the kernel can take
> another exception or not. A cleared MSR_RI flag indicates that the kernel
> cannot.
> 
> Unfortunately when a machine is under high load an SLB miss can occur in
> restore_math() which (with MSR_RI cleared) leads to an unrecoverable exception.
...
> 
> Signed-off-by: Cyril Bur <cyrilbur at gmail.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/6e669f085d595cb6053920832c

cheers