linux-kernel - [PATCH] x86/ACPI/boot: Use FADT version to check support for online capable

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Date:   Wed, 29 Mar 2023 12:45:35 -0500
From:   Mario Limonciello <mario.limonciello@....com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Mario Limonciello <mario.limonciello@....com>
CC:     Eric DeVolder <eric.devolder@...cle.com>,
        Borislav Petkob <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "Dave Hansen" <dave.hansen@...ux.intel.com>, <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, <linux-pm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH] x86/ACPI/boot: Use FADT version to check support for online capable

ACPI 6.3 introduced the online capable bit, and also introduced MADT
version 5.

This was used to distinguish whether the offset storing online capable
could be used. However ACPI 6.2b has MADT version "45" which is for
an errata version of the ACPI 6.2 spec.  This means that the Linux code
for detecting availability of MADT will mistakingly flag ACPI 6.2b as
supporting online capable which is inaccurate as it's an ACPI 6.3 feature.

Instead use the FADT major and minor revision fields to distingush this.

Reported-by: Eric DeVolder <eric.devolder@...cle.com>
Reported-by: Borislav Petkob <bp@...en8.de>
Fixes: aa06e20f1be6 ("x86/ACPI: Don't add CPUs that are not online capable")
Signed-off-by: Mario Limonciello <mario.limonciello@....com>
---
 arch/x86/kernel/acpi/boot.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 1c38174b5f01..e92e3292fef7 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -146,7 +146,10 @@ static int __init acpi_parse_madt(struct acpi_table_header *table)
 
 		pr_debug("Local APIC address 0x%08x\n", madt->address);
 	}
-	if (madt->header.revision >= 5)
+
+	if (acpi_gbl_FADT.header.revision > 6 ||
+	    (acpi_gbl_FADT.header.revision == 6 &&
+	     acpi_gbl_FADT.minor_revision >= 3))
 		acpi_support_online_capable = true;
 
 	default_acpi_madt_oem_check(madt->header.oem_id,
-- 
2.34.1