Re: [Qemu-devel] [PATCH 11/33] pc: acpi: cpuhp-legacy: switch ProcessorID to possible_cpus idx

[Marcel Apfelbaum <marcel@redhat.com>]

On 05/17/2016 05:43 PM, Igor Mammedov wrote:
> In legacy cpu-hotplug ProcessorID == APIC ID is used
> in MADT and cpu-hotplug AML. It was fine as both
> are 8bit and unique. Spec depricated Processor()
> with corresponding ProcessorID and advises to use
> Device() and UID instead of it.
>
> However UID is just 32bit and it can't fit ARM's
> arch_id(MPIDR) which is 64bit. Also in case of
> sparse arch_id() distribution, managment/lookup
> of maps by arch_id(APIC ID/MPIDR) becomes complex
> and expensive.
>
> In preparation to common CPU hotplug with ARM
> and to simplify lookup in possible_cpus[] map
> switch ProcessorID to possible_cpus index in
> MADT.
>
> Legacy cpu-hotplug considerations:
> HW interface of it is APIC ID based bitmask so
> it's impossible to change, also CPON package in
> AML also APIC ID based as well all the methods.
>
> To avoid massive rewrite of AML keep is so and
> just break assumption that ProcessorID == APIC ID,
> ammending CPU_MAT_METHOD to accept APIC ID and
> possible_cpus index, it needs them both to patch
> MADT entry template. Also switch to possible_cpus
> index Processor(ProcessorID) AML.
> That way changes to MADT/AML are minimal and kept
> inside AML/MADT not affecting external interfaces.
>

I vaguely understood the explanation, I'll let Eduardo have a look :)

Thanks,
Marcel

> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> ---
>   hw/acpi/cpu_hotplug.c | 23 +++++++++++++----------
>   hw/i386/acpi-build.c  |  2 +-
>   2 files changed, 14 insertions(+), 11 deletions(-)
>
> diff --git a/hw/acpi/cpu_hotplug.c b/hw/acpi/cpu_hotplug.c
> index 36ea6c2..9d71d2f 100644
> --- a/hw/acpi/cpu_hotplug.c
> +++ b/hw/acpi/cpu_hotplug.c
> @@ -99,7 +99,8 @@ void build_legacy_cpu_hotplug_aml(Aml *ctx, MachineState *machine,
>       int i, apic_idx;
>       Aml *sb_scope = aml_scope("_SB");
>       uint8_t madt_tmpl[8] = {0x00, 0x08, 0x00, 0x00, 0x00, 0, 0, 0};
> -    Aml *cpu_id = aml_arg(0);
> +    Aml *cpu_id = aml_arg(1);
> +    Aml *apic_id = aml_arg(0);
>       Aml *cpu_on = aml_local(0);
>       Aml *madt = aml_local(1);
>       Aml *cpus_map = aml_name(CPU_ON_BITMAP);
> @@ -111,30 +112,31 @@ void build_legacy_cpu_hotplug_aml(Aml *ctx, MachineState *machine,
>
>       /*
>        * _MAT method - creates an madt apic buffer
> -     * cpu_id = Arg0 = Processor ID = Local APIC ID
> +     * apic_id = Arg0 = Local APIC ID
> +     * cpu_id  = Arg1 = Processor ID
>        * cpu_on = Local0 = CPON flag for this cpu
>        * madt = Local1 = Buffer (in madt apic form) to return
>        */
> -    method = aml_method(CPU_MAT_METHOD, 1, AML_NOTSERIALIZED);
> +    method = aml_method(CPU_MAT_METHOD, 2, AML_NOTSERIALIZED);
>       aml_append(method,
> -        aml_store(aml_derefof(aml_index(cpus_map, cpu_id)), cpu_on));
> +        aml_store(aml_derefof(aml_index(cpus_map, apic_id)), cpu_on));
>       aml_append(method,
>           aml_store(aml_buffer(sizeof(madt_tmpl), madt_tmpl), madt));
>       /* Update the processor id, lapic id, and enable/disable status */
>       aml_append(method, aml_store(cpu_id, aml_index(madt, aml_int(2))));
> -    aml_append(method, aml_store(cpu_id, aml_index(madt, aml_int(3))));
> +    aml_append(method, aml_store(apic_id, aml_index(madt, aml_int(3))));
>       aml_append(method, aml_store(cpu_on, aml_index(madt, aml_int(4))));
>       aml_append(method, aml_return(madt));
>       aml_append(sb_scope, method);
>
>       /*
>        * _STA method - return ON status of cpu
> -     * cpu_id = Arg0 = Processor ID = Local APIC ID
> +     * apic_id = Arg0 = Local APIC ID
>        * cpu_on = Local0 = CPON flag for this cpu
>        */
>       method = aml_method(CPU_STATUS_METHOD, 1, AML_NOTSERIALIZED);
>       aml_append(method,
> -        aml_store(aml_derefof(aml_index(cpus_map, cpu_id)), cpu_on));
> +        aml_store(aml_derefof(aml_index(cpus_map, apic_id)), cpu_on));
>       if_ctx = aml_if(cpu_on);
>       {
>           aml_append(if_ctx, aml_return(aml_int(0xF)));
> @@ -243,11 +245,12 @@ void build_legacy_cpu_hotplug_aml(Aml *ctx, MachineState *machine,
>
>           assert(apic_id < ACPI_CPU_HOTPLUG_ID_LIMIT);
>
> -        dev = aml_processor(apic_id, 0, 0, "CP%.02X", apic_id);
> +        dev = aml_processor(i, 0, 0, "CP%.02X", apic_id);
>
>           method = aml_method("_MAT", 0, AML_NOTSERIALIZED);
>           aml_append(method,
> -            aml_return(aml_call1(CPU_MAT_METHOD, aml_int(apic_id))));
> +            aml_return(aml_call2(CPU_MAT_METHOD, aml_int(apic_id), aml_int(i))
> +        ));
>           aml_append(dev, method);
>
>           method = aml_method("_STA", 0, AML_NOTSERIALIZED);
> @@ -268,7 +271,7 @@ void build_legacy_cpu_hotplug_aml(Aml *ctx, MachineState *machine,
>       /* build this code:
>        *   Method(NTFY, 2) {If (LEqual(Arg0, 0x00)) {Notify(CP00, Arg1)} ...}
>        */
> -    /* Arg0 = Processor ID = APIC ID */
> +    /* Arg0 = APIC ID */
>       method = aml_method(AML_NOTIFY_METHOD, 2, AML_NOTSERIALIZED);
>       for (i = 0; i < apic_ids->len; i++) {
>           int apic_id = apic_ids->cpus[i].arch_id;
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index b33fec9..768918f 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -354,7 +354,7 @@ build_madt(GArray *table_data, GArray *linker, PCMachineState *pcms)
>
>           apic->type = ACPI_APIC_PROCESSOR;
>           apic->length = sizeof(*apic);
> -        apic->processor_id = apic_id;
> +        apic->processor_id = i;
>           apic->local_apic_id = apic_id;
>           if (apic_ids->cpus[i].cpu != NULL) {
>               apic->flags = cpu_to_le32(1);
>