[PATCH 09/14] powerpc/rtas: Leave MSR[RI] enabled over RTAS call

[Nicholas Piggin]

PAPR specifies that RTAS may be called with MSR[RI] enabled if the
calling context is recoverable, and RTAS will manage RI as necessary.
Call the rtas entry point with RI enabled, and add a check to ensure
the caller has RI enabled.

Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
---
 arch/powerpc/kernel/rtas.c       |  1 +
 arch/powerpc/kernel/rtas_entry.S | 13 +++----------
 2 files changed, 4 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index 87ede1877816..fece066115f0 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -57,6 +57,7 @@ static noinline void do_enter_rtas(unsigned long args)
 		hard_irq_disable();
 
 		msr = mfmsr();
+		BUG_ON(!(msr & MSR_RI));
 		mtmsr(msr & ~(MSR_IR|MSR_DR));
 		enter_rtas(args);
 		mtmsr(msr);
diff --git a/arch/powerpc/kernel/rtas_entry.S b/arch/powerpc/kernel/rtas_entry.S
index 292551684bbd..72b27b14ccc9 100644
--- a/arch/powerpc/kernel/rtas_entry.S
+++ b/arch/powerpc/kernel/rtas_entry.S
@@ -95,7 +95,7 @@ _GLOBAL(enter_rtas)
 	clrldi	r4,r4,2			/* convert to realmode address */
 	mtlr	r4
 
-	LOAD_REG_IMMEDIATE(r6, MSR_ME)
+	LOAD_REG_IMMEDIATE(r6, MSR_ME|MSR_RI)
 
 	LOAD_REG_ADDR(r4, rtas)
 	ld	r5,RTASENTRY(r4)	/* get the rtas->entry value */
@@ -113,15 +113,8 @@ _ASM_NOKPROBE_SYMBOL(enter_rtas)
 rtas_return_loc:
 	FIXUP_ENDIAN
 
-	/*
-	 * Clear RI and set SF before anything.
-	 */
-	mfmsr	r6
-	li	r0,MSR_RI
-	andc	r6,r6,r0
-	sldi	r0,r0,(MSR_SF_LG - MSR_RI_LG)
-	or	r6,r6,r0
-	sync
+	/* Set SF before anything. */
+	LOAD_REG_IMMEDIATE(r6, MSR_KERNEL & ~(MSR_IR|MSR_DR))
 	mtmsrd	r6
 
 	GET_PACA(r13)
-- 
2.23.0