linux-kernel - [PATCH v1 3/4] powerpc/code-patching: Use jump

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Date:   Tue, 27 Sep 2022 16:33:06 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Gray <bgray@...ux.ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v1 3/4] powerpc/code-patching: Use jump_label for testing freed initmem

Once init is done, initmem is freed forever so no need to
test system_state at every call to patch_instruction().

Use jump_label.

This reduces by 2% the time needed to activate ftrace on an 8xx.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/include/asm/code-patching.h | 2 ++
 arch/powerpc/lib/code-patching.c         | 5 ++++-
 arch/powerpc/mm/mem.c                    | 2 ++
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
index 409483b2d0ce..bccc3a538b9f 100644
--- a/arch/powerpc/include/asm/code-patching.h
+++ b/arch/powerpc/include/asm/code-patching.h
@@ -22,6 +22,8 @@
 #define BRANCH_SET_LINK	0x1
 #define BRANCH_ABSOLUTE	0x2
 
+DECLARE_STATIC_KEY_FALSE(init_mem_is_free);
+
 bool is_offset_in_branch_range(long offset);
 bool is_offset_in_cond_branch_range(long offset);
 int create_branch(ppc_inst_t *instr, const u32 *addr,
diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index 62692c6031bc..ab434c3853c9 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -8,6 +8,7 @@
 #include <linux/init.h>
 #include <linux/cpuhotplug.h>
 #include <linux/uaccess.h>
+#include <linux/jump_label.h>
 
 #include <asm/tlbflush.h>
 #include <asm/page.h>
@@ -193,10 +194,12 @@ static int do_patch_instruction(u32 *addr, ppc_inst_t instr)
 
 #endif /* CONFIG_STRICT_KERNEL_RWX */
 
+__ro_after_init DEFINE_STATIC_KEY_FALSE(init_mem_is_free);
+
 int patch_instruction(u32 *addr, ppc_inst_t instr)
 {
 	/* Make sure we aren't patching a freed init section */
-	if (system_state >= SYSTEM_FREEING_INITMEM && init_section_contains(addr, 4))
+	if (static_branch_likely(&init_mem_is_free) && init_section_contains(addr, 4))
 		return 0;
 
 	return do_patch_instruction(addr, instr);
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 8e301cd8925b..9710d4e0bf08 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -22,6 +22,7 @@
 #include <asm/kasan.h>
 #include <asm/svm.h>
 #include <asm/mmzone.h>
+#include <asm/code-patching.h>
 
 #include <mm/mmu_decl.h>
 
@@ -311,6 +312,7 @@ void free_initmem(void)
 {
 	ppc_md.progress = ppc_printk_progress;
 	mark_initmem_nx();
+	static_branch_enable(&init_mem_is_free);
 	free_initmem_default(POISON_FREE_INITMEM);
 }
 
-- 
2.35.1