linux-kernel - [PATCH] powerpc/8xx: CONFIG_DEBUG_PAGEALLOC requires ITLBmiss for kernel addresses

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Message-Id: <20160203223426.60C681A2446@localhost.localdomain>
Date:	Wed,  3 Feb 2016 23:34:21 +0100 (CET)
From:	Christophe Leroy <christophe.leroy@....fr>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Scott Wood <oss@...error.net>
Cc:	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH] powerpc/8xx: CONFIG_DEBUG_PAGEALLOC requires ITLBmiss for
 kernel addresses

When CONFIG_DEBUG_PAGEALLOC is activated, the initial TLB mapping gets
flushed to track accesses to wrong areas. Therefore, kernel addresses
will also generate ITLB misses.

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
 arch/powerpc/kernel/head_8xx.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 78c1eba..e629e28 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -329,7 +329,7 @@ InstructionTLBMiss:
 	/* If we are faulting a kernel address, we have to use the
 	 * kernel page tables.
 	 */
-#ifdef CONFIG_MODULES
+#if defined(CONFIG_MODULES) || defined (CONFIG_DEBUG_PAGEALLOC)
 	/* Only modules will cause ITLB Misses as we always
 	 * pin the first 8MB of kernel memory */
 	mfspr	r11, SPRN_SRR0	/* Get effective address of fault */
-- 
2.1.0