From: Nicholas Piggin <npiggin@gmail.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: Nicholas Piggin <npiggin@gmail.com>
Subject: [PATCH] powerpc/64s/exception: Fix machine check early corrupting AMR
Date: Sat, 22 Jun 2019 08:55:54 +1000 [thread overview]
Message-ID: <20190621225554.1913-1-npiggin@gmail.com> (raw)
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@russell.cc>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
arch/powerpc/kernel/exceptions-64s.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 6b86055e5251..73ba246ca11d 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -315,7 +315,7 @@ TRAMP_REAL_BEGIN(machine_check_common_early)
mfspr r11,SPRN_DSISR /* Save DSISR */
std r11,_DSISR(r1)
std r9,_CCR(r1) /* Save CR in stackframe */
- kuap_save_amr_and_lock r9, r10, cr1
+ /* We don't touch AMR here, we never go to virtual mode */
/* Save r9 through r13 from EXMC save area to stack frame. */
EXCEPTION_PROLOG_COMMON_2(PACA_EXMC)
mfmsr r11 /* get MSR value */
--
2.20.1
next reply other threads:[~2019-06-21 22:58 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-21 22:55 Nicholas Piggin [this message]
2019-06-29 11:37 ` [PATCH] powerpc/64s/exception: Fix machine check early corrupting AMR Michael Ellerman
2019-06-29 12:25 ` Michael Ellerman
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