On Tue, 11 Apr 2023 18:00:49 +0200
Igor Mammedov <imamm...@redhat.com> wrote:
> On Tue, 28 Mar 2023 11:59:26 -0400
> Eric DeVolder <eric.devol...@oracle.com> wrote:
>
> > Currently i386 QEMU generates MADT revision 3, and reports
> > MADT revision 1. ACPI 6.3 introduces MADT revision 5.
> >
> > For MADT revision 4, that introduces ARM GIC structures, which do
> > not apply to i386.
> >
> > For MADT revision 5, the Local APIC flags introduces the Online
> > Capable bitfield.
> >
> > Making MADT generate and report revision 5 will solve problems with
> > CPU hotplug (the Online Capable flag indicates hotpluggable CPUs).
>
> So spec mandates 3 possible states
> 00t - not present and not can't be added later ever
> 01t - present
> 10t - not present but might be added later
> and outlawed 11t combination
>
> 00t - doesn't make much sense (i.e. why put such entry in MADT in the 1st
> place)
>
> but looking at kernel commit aa06e20f1be, it looks like
> ACPI_MADT_ONLINE_CAPABLE was introduced to accommodate
> firmware/hw folks who would stuff MADT with LAPIC entries
> for all possible CPU models, and then patch it depending on
> actually used CPU model instead of dynamically creating LAPIC
> entries. (insane)
on second thought, QEMU doesn't need rev 5 MADT with this flag complications.
Also I see that kernel side fix ended up in checking ACPI spec version instead
of dealing with MADT revisions mess.
So for x86 lets bump revision to 3 or 4 to be in sync with
what QEMU actually uses.
>
>
> > Signed-off-by: Eric DeVolder <eric.devol...@oracle.com>
> > ---
> > hw/i386/acpi-common.c | 13 ++++++++++---
> > 1 file changed, 10 insertions(+), 3 deletions(-)
> >
> > diff --git a/hw/i386/acpi-common.c b/hw/i386/acpi-common.c
> > index 52e5c1439a..1e3a13a36c 100644
> > --- a/hw/i386/acpi-common.c
> > +++ b/hw/i386/acpi-common.c
> > @@ -38,8 +38,15 @@ void pc_madt_cpu_entry(int uid, const CPUArchIdList
> > *apic_ids,
> > {
> > uint32_t apic_id = apic_ids->cpus[uid].arch_id;
> > /* Flags – Local APIC Flags */
> > - uint32_t flags = apic_ids->cpus[uid].cpu != NULL || force_enabled ?
> > - 1 /* Enabled */ : 0;
> > + bool enabled = apic_ids->cpus[uid].cpu != NULL || force_enabled ?
> > + true /* Enabled */ : false;
> > + /*
> > + * ACPI 6.3 5.2.12.2 Local APIC Flags: OnlineCapable must be 0
> > + * if Enabled is set.
> > + */
> > + bool onlinecapable = enabled ? false : true; /* Online Capable */
>
> > + uint32_t flags = onlinecapable ? 0x2 : 0x0 |
> > + enabled ? 0x1 : 0x0;
> align the last line with onlinecapable ....'
>
> move /* Enabled */ and /* Online Capable */ comments right to magic values
> i.e. onlinecapable ? 0x2 : 0x0 | /* Online Capable */ ...
>
> >
> > /* ACPI spec says that LAPIC entry for non present
> > * CPU may be omitted from MADT or it must be marked
> > @@ -102,7 +109,7 @@ void acpi_build_madt(GArray *table_data, BIOSLinker
> > *linker,
> > MachineClass *mc = MACHINE_GET_CLASS(x86ms);
> > const CPUArchIdList *apic_ids =
> > mc->possible_cpu_arch_ids(MACHINE(x86ms));
> > AcpiDeviceIfClass *adevc = ACPI_DEVICE_IF_GET_CLASS(adev);
> > - AcpiTable table = { .sig = "APIC", .rev = 1, .oem_id = oem_id,
> > + AcpiTable table = { .sig = "APIC", .rev = 5, .oem_id = oem_id,
> > .oem_table_id = oem_table_id };
> >
> > acpi_table_begin(&table, table_data);
>
