[PATCH 5.10 074/145] powerpc/32s: Fix RTAS machine check with VMAP stack

[Greg Kroah-Hartman]

From: Christophe Leroy <christophe.leroy@xxxxxxxxxx>

commit 98bf2d3f4970179c702ef64db658e0553bc6ef3a upstream.

When we have VMAP stack, exception prolog 1 sets r1, not r11.

When it is not an RTAS machine check, don't trash r1 because it is
needed by prolog 1.

Fixes: da7bb43ab9da ("powerpc/32: Fix vmap stack - Properly set r1 before activating MMU")
Fixes: d2e006036082 ("powerpc/32: Use SPRN_SPRG_SCRATCH2 in exception prologs")
Cc: stable@xxxxxxxxxxxxxxx # v5.10+
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
[mpe: Squash in fixup for RTAS machine check from Christophe]
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/bc77d61d1c18940e456a2dee464f1e2eda65a3f0.1608621048.git.christophe.leroy@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/powerpc/kernel/head_book3s_32.S |    9 +++++++++
 1 file changed, 9 insertions(+)

--- a/arch/powerpc/kernel/head_book3s_32.S
+++ b/arch/powerpc/kernel/head_book3s_32.S
@@ -262,10 +262,19 @@ __secondary_hold_acknowledge:
 MachineCheck:
 	EXCEPTION_PROLOG_0
 #ifdef CONFIG_PPC_CHRP
+#ifdef CONFIG_VMAP_STACK
+	mtspr	SPRN_SPRG_SCRATCH2,r1
+	mfspr	r1, SPRN_SPRG_THREAD
+	lwz	r1, RTAS_SP(r1)
+	cmpwi	cr1, r1, 0
+	bne	cr1, 7f
+	mfspr	r1, SPRN_SPRG_SCRATCH2
+#else
 	mfspr	r11, SPRN_SPRG_THREAD
 	lwz	r11, RTAS_SP(r11)
 	cmpwi	cr1, r11, 0
 	bne	cr1, 7f
+#endif
 #endif /* CONFIG_PPC_CHRP */
 	EXCEPTION_PROLOG_1 for_rtas=1
 7:	EXCEPTION_PROLOG_2