powerpc/tm: Clear MSR RI in non-recoverable TM code

When we treclaim and trecheckpoint there's an unavoidable period when r1
will not be a valid kernel stack pointer.

This patch clears the MSR recoverable interrupt (RI) bit over these
regions to indicate we have an invalid kernel stack pointer.

For treclaim, the region over which we clear MSR RI is larger than
required to avoid the need for an extra costly mtmsrd.

Thanks to Paulus for suggesting this change.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --git a/arch/powerpc/kernel/tm.S b/arch/powerpc/kernel/tm.S
index 2da67e7a16d58650e10a0b6113b705bd88a6f2d3..51be8fb2480313610b5971b6ef70a89f58f794a2 100644 (file)
--- a/arch/powerpc/kernel/tm.S
+++ b/arch/powerpc/kernel/tm.S
@@ -112,9 +112,18 @@ _GLOBAL(tm_reclaim)
        std     r3, STACK_PARAM(0)(r1)
        SAVE_NVGPRS(r1)
 
+       /* We need to setup MSR for VSX register save instructions.  Here we
+        * also clear the MSR RI since when we do the treclaim, we won't have a
+        * valid kernel pointer for a while.  We clear RI here as it avoids
+        * adding another mtmsr closer to the treclaim.  This makes the region
+        * maked as non-recoverable wider than it needs to be but it saves on
+        * inserting another mtmsrd later.
+        */
        mfmsr   r14
        mr      r15, r14
        ori     r15, r15, MSR_FP
+       li      r16, MSR_RI
+       andc    r15, r15, r16
        oris    r15, r15, MSR_VEC@h
 #ifdef CONFIG_VSX
        BEGIN_FTR_SECTION
@@ -349,9 +358,10 @@ restore_gprs:
        mtcr    r5
        mtxer   r6
 
-       /* MSR and flags:  We don't change CRs, and we don't need to alter
-        * MSR.
+       /* Clear the MSR RI since we are about to change R1.  EE is already off
         */
+       li      r4, 0
+       mtmsrd  r4, 1
 
        REST_4GPRS(0, r7)                       /* GPR0-3 */
        REST_GPR(4, r7)                         /* GPR4-6 */
@@ -377,6 +387,10 @@ restore_gprs:
        GET_PACA(r13)
        GET_SCRATCH0(r1)
 
+       /* R1 is restored, so we are recoverable again.  EE is still off */
+       li      r4, MSR_RI
+       mtmsrd  r4, 1
+
        REST_NVGPRS(r1)
 
        addi    r1, r1, TM_FRAME_SIZE