linux-kernel - [PATCH v2 2/2] powerpc/8xx: Map a second 8M text page at startup when needed.

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Message-Id: <c53f0e44ea783306e72e51e1f33a2bb5aea6f800.1547801451.git.christophe.leroy@c-s.fr>
Date:   Mon, 21 Jan 2019 11:34:38 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v2 2/2] powerpc/8xx: Map a second 8M text page at startup when
 needed.

Some debug setup like CONFIG_KASAN generate huge
kernels with text size over the 8M limit.

This patch maps a second 8M page when _einittext is over 8M.

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
 v2: Using IS_ENABLED() instead of #ifdef in 8xx_mmu.c

 arch/powerpc/kernel/head_8xx.S | 27 +++++++++++++++++++++++++--
 arch/powerpc/mm/8xx_mmu.c      |  3 +++
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 20cc816b3508..3b3b7846247f 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -337,8 +337,8 @@ InstructionTLBMiss:
 	rlwinm	r10, r10, 16, 0xfff8
 	cmpli	cr0, r10, PAGE_OFFSET@h
 #ifndef CONFIG_PIN_TLB_TEXT
-	/* It is assumed that kernel code fits into the first 8M page */
-0:	cmpli	cr7, r10, (PAGE_OFFSET + 0x0800000)@h
+	/* It is assumed that kernel code fits into the two first 8M pages */
+0:	cmpli	cr7, r10, (PAGE_OFFSET + 0x1000000)@h
 	patch_site	0b, patch__itlbmiss_linmem_top
 #endif
 #endif
@@ -908,6 +908,29 @@ initial_mmu:
 	li	r8, MI_BOOTINIT		/* Create RPN for address 0 */
 	mtspr	SPRN_MI_RPN, r8		/* Store TLB entry */
 
+	/* Map a second 8M page if needed */
+	lis	r9, _einittext@h
+	oris	r9, r9, _einittext@l
+	cmpli	cr0, r9, (PAGE_OFFSET + 0x8000000)@h
+	blt	1f
+
+#ifdef CONFIG_PIN_TLB_TEXT
+	lis	r8, MI_RSV4I@h
+	ori	r8, r8, 0x1d00
+
+	mtspr	SPRN_MI_CTR, r8	/* Set instruction MMU control */
+#endif
+
+	lis	r8, (KERNELBASE + 0x800000)@h	/* Create vaddr for TLB */
+	ori	r8, r8, MI_EVALID	/* Mark it valid */
+	mtspr	SPRN_MI_EPN, r8
+	li	r8, MI_PS8MEG /* Set 8M byte page */
+	ori	r8, r8, MI_SVALID	/* Make it valid */
+	mtspr	SPRN_MI_TWC, r8
+	li	r8, MI_BOOTINIT		/* Create RPN for address 0 */
+	addis	r8, r8, 0x80
+	mtspr	SPRN_MI_RPN, r8		/* Store TLB entry */
+1:
 	lis	r8, MI_APG_INIT@h	/* Set protection modes */
 	ori	r8, r8, MI_APG_INIT@l
 	mtspr	SPRN_MI_AP, r8
diff --git a/arch/powerpc/mm/8xx_mmu.c b/arch/powerpc/mm/8xx_mmu.c
index 92b677faea8c..b5f6d794281d 100644
--- a/arch/powerpc/mm/8xx_mmu.c
+++ b/arch/powerpc/mm/8xx_mmu.c
@@ -112,6 +112,9 @@ unsigned long __init mmu_mapin_ram(unsigned long top)
 			mmu_patch_cmp_limit(&patch__itlbmiss_linmem_top, 0);
 	} else {
 		mapped = top & ~(LARGE_PAGE_SIZE_8M - 1);
+		if (!IS_ENABLED(CONFIG_PIN_TLB_TEXT))
+			mmu_patch_cmp_limit(&patch__itlbmiss_linmem_top,
+					    _ALIGN(__pa(_einittext), 8 << 20));
 	}
 
 	mmu_patch_cmp_limit(&patch__dtlbmiss_linmem_top, mapped);
-- 
2.13.3