Messages in this thread | | | Date | Wed, 29 Mar 2023 14:35:41 -0500 | Subject | Re: [PATCH 1/1] x86/acpi: acpi_is_processor_usable() dropping possible cpus | From | "Limonciello, Mario" <> |
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On 3/27/2023 14:10, Eric DeVolder wrote: > The logic in acpi_is_processor_usable() requires the Online Capable > bit be set for hotpluggable cpus. The Online Capable bit is > introduced in ACPI 6.3 and MADT.revision 5. > > However, as currently coded, for MADT.revision < 5, > acpi_is_processor_usable() no longer allows for possible hot > pluggable cpus, which is a regressive change in behavior. > > This patch restores the behavior where for MADT.revision < 5, the > presence of the lapic/x2apic structure implies a possible hotpluggable > cpu. > > Fixes: e2869bd7af60 ("x86/acpi/boot: Do not register processors that cannot be onlined for x2APIC") > Suggested-by: Miguel Luis <miguel.luis@oracle.com> > Suggested-by: Boris Ostrovsky <boris.ovstrosky@oracle.com> > Signed-off-by: Eric DeVolder <eric.devolder@oracle.com> > ---
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com> Tested-by: David R <david@unsolicited.net> Link: https://lore.kernel.org/all/a15c6a64-dcd7-b102-9d9f-0225dfa1172b@unsolicited.net/T/
> arch/x86/kernel/acpi/boot.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c > index 1c38174b5f01..7b5b8ed018b0 100644 > --- a/arch/x86/kernel/acpi/boot.c > +++ b/arch/x86/kernel/acpi/boot.c > @@ -193,7 +193,13 @@ 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)) > + /* > + * Prior to MADT.revision 5, the presence of the Local x2/APIC > + * structure _implicitly_ noted a possible hotpluggable cpu. > + * Starting with MADT.revision 5, the Online Capable bit > + * _explicitly_ indicates a hotpluggable cpu. > + */ > + if (!acpi_support_online_capable || (lapic_flags & ACPI_MADT_ONLINE_CAPABLE)) > return true; > > return false;
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