[PATCH] powerpc/64s/exception: Fix machine check early corrupting AMR

[Michael Ellerman]

On Fri, 2019-06-21 at 22:55:54 UTC, Nicholas Piggin wrote:
> The early machine check runs in real mode, so locking is unnecessary.
> Worse, the windup does not restore AMR, so this can result in a false
> KUAP fault after a recoverable machine check hits inside a user copy
> operation.
> 
> Fix this similarly to HMI by just avoiding the kuap lock in the
> early machine check handler (it will be set by the late handler that
> runs in virtual mode if that runs). If the virtual mode handler is
> reached, it will lock and restore the AMR.
> 
> Fixes: 890274c2dc4c0 ("powerpc/64s: Implement KUAP for Radix MMU")
> Cc: Russell Currey <ruscur at russell.cc>
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/e13e7cd4c0c1cc9984d9b6a8663e10d76b53f2aa

cheers