[PATCH v2 05/23] arm64: cpufeature: Check arm64_ftr_regs[] before the first store

[Will Deacon]

From: Fuad Tabba <fuad.tabba at linux.dev>

sort_ftr_regs() sorts nothing. It checks that arm64_ftr_regs[] is in
sys_id order, which the binary search in get_arm64_ftr_reg() relies on,
and that no register's fields overlap. It runs at the top of
init_cpu_features(), after the boot CPU's __cpuinfo_store_cpu(). A
subsequent patch makes __cpuinfo_store_cpu() look registers up in the
table.

Rename it validate_ftr_regs() and call it from smp_prepare_boot_cpu(),
ahead of cpuinfo_store_boot_cpu().

Suggested-by: Will Deacon <will at kernel.org>
Signed-off-by: Fuad Tabba <fuad.tabba at linux.dev>
Signed-off-by: Will Deacon <will at kernel.org>
---
 arch/arm64/include/asm/cpu.h   | 1 +
 arch/arm64/kernel/cpufeature.c | 5 +----
 arch/arm64/kernel/smp.c        | 2 ++
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/cpu.h b/arch/arm64/include/asm/cpu.h
index 3c008821219c..f332fbd8e46d 100644
--- a/arch/arm64/include/asm/cpu.h
+++ b/arch/arm64/include/asm/cpu.h
@@ -75,6 +75,7 @@ DECLARE_PER_CPU(struct cpuinfo_arm64, cpu_data);
 void cpuinfo_store_cpu(void);
 void __init cpuinfo_store_boot_cpu(void);
 
+void __init validate_ftr_regs(void);
 void __init init_cpu_features(struct cpuinfo_arm64 *info);
 void update_cpu_features(int cpu, struct cpuinfo_arm64 *info,
 				 struct cpuinfo_arm64 *boot);
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 32102c3912fa..727e1665c987 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -962,7 +962,7 @@ s64 arm64_ftr_safe_value(const struct arm64_ftr_bits *ftrp, s64 new,
 	return ret;
 }
 
-static void __init sort_ftr_regs(void)
+void __init validate_ftr_regs(void)
 {
 	unsigned int i;
 
@@ -1207,9 +1207,6 @@ bool gmid_el1_accessible(const struct cpuinfo_arm64 *info)
 
 void __init init_cpu_features(struct cpuinfo_arm64 *info)
 {
-	/* Before we start using the tables, make sure it is sorted */
-	sort_ftr_regs();
-
 	init_cpu_ftr_reg(SYS_CTR_EL0, info->reg_ctr);
 	init_cpu_ftr_reg(SYS_DCZID_EL0, info->reg_dczid);
 	init_cpu_ftr_reg(SYS_CNTFRQ_EL0, info->reg_cntfrq);
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index a61dc3016a11..eac217b9ebf1 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -455,6 +455,8 @@ void __init smp_prepare_boot_cpu(void)
 	 */
 	set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
 
+	/* Check arm64_ftr_regs[] before anything looks registers up in it. */
+	validate_ftr_regs();
 	cpuinfo_store_boot_cpu();
 	setup_boot_cpu_features();
 
-- 
2.56.0.385.gd3acb90ef8-goog