[PATCH] x86/acpi: Fix LAPIC/x2APIC parsing order

[Zhang Rui <rui.zhang@xxxxxxxxx>]

On some systems, the same CPU (with same APIC ID) is assigned with a
different logical CPU id after commit ec9aedb2aa1a ("x86/acpi: Ignore
invalid x2APIC entries").

This means Linux enumerates the CPUs in a different order and it is a
violation of https://uefi.org/specs/ACPI/6.5/05_ACPI_Software_Programming_Model.html#madt-processor-local-apic-sapic-structure-entry-order,

  "OSPM should initialize processors in the order that they appear in
   the MADT"

The offending commit wants to ignore x2APIC entries with APIC ID < 255
when valid LAPIC entries exist, so it parses all LAPIC entries before
parsing any x2APIC entries. This breaks the CPU enumeration order for
systems that have x2APIC entries listed before LAPIC entries in MADT.

Fix the problem by checking the valid LAPIC entries separately, before
parsing any LAPIC/x2APIC entries.

Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Jim Mattson <jmattson@xxxxxxxxxx>
Closes: https://lore.kernel.org/all/20241010213136.668672-1-jmattson@xxxxxxxxxx/
Fixes: ec9aedb2aa1a ("x86/acpi: Ignore invalid x2APIC entries")
Signed-off-by: Zhang Rui <rui.zhang@xxxxxxxxx>
---
 arch/x86/kernel/acpi/boot.c | 50 +++++++++++++++++++++++++++++++++----
 1 file changed, 45 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 4efecac49863..c70b86f1f295 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -226,6 +226,28 @@ acpi_parse_x2apic(union acpi_subtable_headers *header, const unsigned long end)
 	return 0;
 }
 
+static int __init
+acpi_check_lapic(union acpi_subtable_headers *header, const unsigned long end)
+{
+	struct acpi_madt_local_apic *processor = NULL;
+
+	processor = (struct acpi_madt_local_apic *)header;
+
+	if (BAD_MADT_ENTRY(processor, end))
+		return -EINVAL;
+
+	/* Ignore invalid ID */
+	if (processor->id == 0xff)
+		return 0;
+
+	/* Ignore processors that can not be onlined */
+	if (!acpi_is_processor_usable(processor->lapic_flags))
+		return 0;
+
+	has_lapic_cpus = true;
+	return 0;
+}
+
 static int __init
 acpi_parse_lapic(union acpi_subtable_headers * header, const unsigned long end)
 {
@@ -257,7 +279,6 @@ acpi_parse_lapic(union acpi_subtable_headers * header, const unsigned long end)
 			       processor->processor_id, /* ACPI ID */
 			       processor->lapic_flags & ACPI_MADT_ENABLED);
 
-	has_lapic_cpus = true;
 	return 0;
 }
 
@@ -1029,6 +1050,8 @@ static int __init early_acpi_parse_madt_lapic_addr_ovr(void)
 static int __init acpi_parse_madt_lapic_entries(void)
 {
 	int count, x2count = 0;
+	struct acpi_subtable_proc madt_proc[2];
+	int ret;
 
 	if (!boot_cpu_has(X86_FEATURE_APIC))
 		return -ENODEV;
@@ -1037,10 +1060,27 @@ static int __init acpi_parse_madt_lapic_entries(void)
 				      acpi_parse_sapic, MAX_LOCAL_APIC);
 
 	if (!count) {
-		count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_APIC,
-					acpi_parse_lapic, MAX_LOCAL_APIC);
-		x2count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_X2APIC,
-					acpi_parse_x2apic, MAX_LOCAL_APIC);
+		/* Check if there are valid LAPIC entries */
+		acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_APIC, acpi_check_lapic, MAX_LOCAL_APIC);
+
+		/*
+		 * Enumerate the APIC IDs in the order that they appear in the
+		 * MADT, no matter LAPIC entry or x2APIC entry is used.
+		 */
+		memset(madt_proc, 0, sizeof(madt_proc));
+		madt_proc[0].id = ACPI_MADT_TYPE_LOCAL_APIC;
+		madt_proc[0].handler = acpi_parse_lapic;
+		madt_proc[1].id = ACPI_MADT_TYPE_LOCAL_X2APIC;
+		madt_proc[1].handler = acpi_parse_x2apic;
+		ret = acpi_table_parse_entries_array(ACPI_SIG_MADT,
+				sizeof(struct acpi_table_madt),
+				madt_proc, ARRAY_SIZE(madt_proc), MAX_LOCAL_APIC);
+		if (ret < 0) {
+			pr_err("Error parsing LAPIC/X2APIC entries\n");
+			return ret;
+		}
+		count = madt_proc[0].count;
+		x2count = madt_proc[1].count;
 	}
 	if (!count && !x2count) {
 		pr_err("No LAPIC entries present\n");
-- 
2.34.1