| Message ID | 20210812051657.28605-1-mario.limonciello@amd.com |
|---|---|
| State | New |
| Headers | show |
| Series | x86/acpi: Don't add CPUs that are not online capable | expand |
On 2021/8/12 13:16, Mario Limonciello wrote: > 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. > > The ACPI spec is clear that the Online Capable bit in the > MADT should be used to determine whether or not a CPU is hotplug > capable when the enabled bit is not set. This was introduced in ACPI 6.3 spec, which means ACPI 6.2 and earlier versions don't include the "Online Capable bit". > > Link: https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/05_ACPI_Software_Programming_Model/ACPI_Software_Programming_Model.html?#local-apic-flags > Reviewed-by: Alex Deucher <alexander.deucher@amd.com> > Reviewed-by: Huang Rui <ray.huang@amd.com> > Signed-off-by: Mario Limonciello <mario.limonciello@amd.com> > --- > arch/x86/kernel/acpi/boot.c | 6 ++++++ > include/acpi/actbl2.h | 1 + > 2 files changed, 7 insertions(+) > > diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c > index e55e0c1fad8c..eeb10b27d6de 100644 > --- a/arch/x86/kernel/acpi/boot.c > +++ b/arch/x86/kernel/acpi/boot.c > @@ -239,6 +239,12 @@ 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 (!(processor->lapic_flags & ACPI_MADT_ENABLED)) { > + if (!(processor->lapic_flags & ACPI_MADT_ONLINE_CAPABLE)) > + return 0; > + } For firmware using ACPI 6.2 and early versions, the ACPI_MADT_ONLINE_CAPABLE bit is reserved as zero, so if we set CPU as disabled, the code here will always return 0 in those firmwares. > + > /* > * We need to register disabled CPU as well to permit > * counting disabled CPUs. This allows us to size So we will not register the disabled CPU and will break CPU hotplug features. I think we need to consider the compatibility with old versions of firmware. Thanks Hanjun
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c index e55e0c1fad8c..eeb10b27d6de 100644 --- a/arch/x86/kernel/acpi/boot.c +++ b/arch/x86/kernel/acpi/boot.c @@ -239,6 +239,12 @@ 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 (!(processor->lapic_flags & ACPI_MADT_ENABLED)) { + if (!(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 diff --git a/include/acpi/actbl2.h b/include/acpi/actbl2.h index 2069ac38a4e2..fae45e383987 100644 --- a/include/acpi/actbl2.h +++ b/include/acpi/actbl2.h @@ -808,6 +808,7 @@ struct acpi_madt_multiproc_wakeup_mailbox { /* MADT Local APIC flags */ #define ACPI_MADT_ENABLED (1) /* 00: Processor is usable if set */ +#define ACPI_MADT_ONLINE_CAPABLE (2) /* 01: System HW supports enabling processor at runtime */ /* MADT MPS INTI flags (inti_flags) */