linux-kernel - [RFC PATCH 1/2] x86/acpi: Improve code readablity of early madt processing

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Message-ID: <20200122034723.1863-2-caoj.fnst@cn.fujitsu.com>
Date:   Wed, 22 Jan 2020 11:47:22 +0800
From:   Cao jin <caoj.fnst@...fujitsu.com>
To:     <x86@...nel.org>, <linux-pm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     <rjw@...ysocki.net>, <len.brown@...el.com>, <pavel@....cz>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
        <hpa@...or.com>
Subject: [RFC PATCH 1/2] x86/acpi: Improve code readablity of early madt processing

Current processing logic is confusing.

Return value of early_acpi_parse_madt_lapic_addr_ovr() indicates error(< 0),
parsed entry number(>= 0). So, it makes no sense to initialize acpi_lapic &
smp_found_config seeing no override entry, instead, initialize them seeing
MADT.

Put register_lapic_address() into override entry processing doesn't make
sense either.

Improved all the related comments too.

Signed-off-by: Cao jin <caoj.fnst@...fujitsu.com>
---
 arch/x86/kernel/acpi/boot.c | 28 ++++++++++------------------
 1 file changed, 10 insertions(+), 18 deletions(-)

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 04205ce127a1..2131035bba98 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -1003,11 +1003,7 @@ static int __init acpi_parse_fadt(struct acpi_table_header *table)
 }
 
 #ifdef	CONFIG_X86_LOCAL_APIC
-/*
- * Parse LAPIC entries in MADT
- * returns 0 on success, < 0 on error
- */
-
+/* Returns >= 0 on success, indicates parsed entry number; < 0 on error. */
 static int __init early_acpi_parse_madt_lapic_addr_ovr(void)
 {
 	int count;
@@ -1025,11 +1021,8 @@ static int __init early_acpi_parse_madt_lapic_addr_ovr(void)
 	if (count < 0) {
 		printk(KERN_ERR PREFIX
 		       "Error parsing LAPIC address override entry\n");
-		return count;
 	}
 
-	register_lapic_address(acpi_lapic_addr);
-
 	return count;
 }
 
@@ -1234,19 +1227,16 @@ static inline int acpi_parse_madt_ioapic_entries(void)
 static void __init early_acpi_process_madt(void)
 {
 #ifdef CONFIG_X86_LOCAL_APIC
-	int error;
+	int ret;
 
 	if (!acpi_table_parse(ACPI_SIG_MADT, acpi_parse_madt)) {
+		/* Found MADT */
+		acpi_lapic = 1;
+		smp_found_config = 1;
 
-		/*
-		 * Parse MADT LAPIC entries
-		 */
-		error = early_acpi_parse_madt_lapic_addr_ovr();
-		if (!error) {
-			acpi_lapic = 1;
-			smp_found_config = 1;
-		}
-		if (error == -EINVAL) {
+		/* See if override entry exists. */
+		ret = early_acpi_parse_madt_lapic_addr_ovr();
+		if (ret == -EINVAL) {
 			/*
 			 * Dell Precision Workstation 410, 610 come here.
 			 */
@@ -1254,6 +1244,8 @@ static void __init early_acpi_process_madt(void)
 			       "Invalid BIOS MADT, disabling ACPI\n");
 			disable_acpi();
 		}
+
+		register_lapic_address(acpi_lapic_addr);
 	}
 #endif
 }
-- 
2.21.0