x86/ACPI: Don't add CPUs that are not online capable

A number of systems are showing "hotplug capable" CPUs when they
are not really hotpluggable.  This is because the MADT has extra
CPU entries to support different CPUs that may be inserted into
the socket with different numbers of cores.

Starting with ACPI 6.3 the spec has an Online Capable bit in the
MADT used to determine whether or not a CPU is hotplug capable
when the enabled bit is not set.

Link: https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/05_ACPI_Software_Programming_Model/ACPI_Software_Programming_Model.html?#local-apic-flags
Signed-off-by: Mario Limonciello <[email protected]>
Signed-off-by: Rafael J. Wysocki <[email protected]>

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 14bcd59bcdee269ef47b7f398c1f5437cc49ff45..5b6d1a95776f08cb8995492874430ad1fbc201c3 100644 (file)
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -62,6 +62,7 @@ int acpi_fix_pin2_polarity __initdata;
 
 #ifdef CONFIG_X86_LOCAL_APIC
 static u64 acpi_lapic_addr __initdata = APIC_DEFAULT_PHYS_BASE;
+static bool acpi_support_online_capable;
 #endif
 
 #ifdef CONFIG_X86_IO_APIC
@@ -138,6 +139,8 @@ 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)
+               acpi_support_online_capable = true;
 
        default_acpi_madt_oem_check(madt->header.oem_id,
                                    madt->header.oem_table_id);
@@ -239,6 +242,12 @@ acpi_parse_lapic(union acpi_subtable_headers * header, const unsigned long end)
        if (processor->id == 0xff)
                return 0;
 
+       /* don't register processors that can not be onlined */
+       if (acpi_support_online_capable &&
+           !(processor->lapic_flags & ACPI_MADT_ENABLED) &&
+           !(processor->lapic_flags & ACPI_MADT_ONLINE_CAPABLE))
+               return 0;
+
        /*
         * We need to register disabled CPU as well to permit
         * counting disabled CPUs. This allows us to size