Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Thu, 5 Jan 2023 18:09:59 +0100 | Subject | Re: [PATCH v2] x86/acpi/boot: Do not register processors that cannot be onlined for x2apic |
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On Thu, Jan 5, 2023 at 5:11 AM Kishon Vijay Abraham I <kvijayab@amd.com> wrote: > > Section 5.2.12.12 Processor Local x2APIC Structure in the ACPI v6.5 > spec mandates that both "enabled" and "online capable" Local APIC Flags > should be used to determine if the processor is usable or not. > > However, Linux doesn't use the "online capable" flag for x2APIC to > determine if the processor is usable. As a result, cpu_possible_mask has > incorrect value and results in more memory getting allocated for per_cpu > variables than it is going to be used. > > Make sure Linux parses both "enabled" and "online capable" flags for > x2APIC to correctly determine if the processor is usable. > > Fixes: aa06e20f1be6 ("x86/ACPI: Don't add CPUs that are not online capable") > Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de> > Reported-by: Leo Duran <leo.duran@amd.com> > Signed-off-by: Kishon Vijay Abraham I <kvijayab@amd.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> --- > Changes from v1: > 1) Changed the ACPI spec version to 6.5 in the commit log > 2) Changed the Fixes tag to point to commit aa06e20f1be6 > 3) Added "Reported-by: Leo Duran <leo.duran@amd.com>" > arch/x86/kernel/acpi/boot.c | 19 ++++++++++++++++--- > 1 file changed, 16 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c > index 907cc98b1938..518bda50068c 100644 > --- a/arch/x86/kernel/acpi/boot.c > +++ b/arch/x86/kernel/acpi/boot.c > @@ -188,6 +188,17 @@ static int acpi_register_lapic(int id, u32 acpiid, u8 enabled) > return cpu; > } > > +static bool __init acpi_is_processor_usable(u32 lapic_flags) > +{ > + if (lapic_flags & ACPI_MADT_ENABLED) > + return true; > + > + if (acpi_support_online_capable && (lapic_flags & ACPI_MADT_ONLINE_CAPABLE)) > + return true; > + > + return false; > +} > + > static int __init > acpi_parse_x2apic(union acpi_subtable_headers *header, const unsigned long end) > { > @@ -212,6 +223,10 @@ acpi_parse_x2apic(union acpi_subtable_headers *header, const unsigned long end) > if (apic_id == 0xffffffff) > return 0; > > + /* don't register processors that cannot be onlined */ > + if (!acpi_is_processor_usable(processor->lapic_flags)) > + return 0; > + > /* > * We need to register disabled CPU as well to permit > * counting disabled CPUs. This allows us to size > @@ -250,9 +265,7 @@ acpi_parse_lapic(union acpi_subtable_headers * header, const unsigned long end) > 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)) > + if (!acpi_is_processor_usable(processor->lapic_flags)) > return 0; > > /* > -- > 2.34.1 >
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