This is a note to let you know that I've just added the patch titled
x86/ACPI: Don't add CPUs that are not online capable
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-acpi-don-t-add-cpus-that-are-not-online-capable.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 93c81745f8a495babd9b08f8be0cd36dab9cdf7a
Author: Mario Limonciello <mario.limonciello@xxxxxxx>
Date: Wed Sep 8 16:41:46 2021 -0500
x86/ACPI: Don't add CPUs that are not online capable
[ Upstream commit aa06e20f1be628186f0c2dcec09ea0009eb69778 ]
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 <mario.limonciello@xxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Stable-dep-of: 128b0c9781c9 ("x86/i8259: Skip probing when ACPI/MADT advertises PCAT compatibility")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 94ac7402c1ac2..0d01e7f5078c2 100644
--- 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
