Re: [PATCH 5/8] x86: acpi: let the firmware handle pending "CPU remove" events in SMM

[Ankur Arora]

On 2020-12-04 9:09 a.m., Igor Mammedov wrote:
> if firmware and QEMU negotiated CPU hotunplug support, generate
> _EJ0 method so that it will mark CPU for removal by firmware and
> pass control to it by triggering SMI.
>
> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> ---
>   include/hw/acpi/cpu.h |  1 +
>   hw/acpi/cpu.c         | 15 +++++++++++++--
>   hw/i386/acpi-build.c  |  1 +
>   3 files changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/include/hw/acpi/cpu.h b/include/hw/acpi/cpu.h
> index d71edde456..999caaf510 100644
> --- a/include/hw/acpi/cpu.h
> +++ b/include/hw/acpi/cpu.h
> @@ -51,6 +51,7 @@ void cpu_hotplug_hw_init(MemoryRegion *as, Object *owner,
>   typedef struct CPUHotplugFeatures {
>       bool acpi_1_compatible;
>       bool has_legacy_cphp;
> +    bool fw_unplugs_cpu;
>       const char *smi_path;
>   } CPUHotplugFeatures;
>   
> diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c
> index 811218f673..bded2a837f 100644
> --- a/hw/acpi/cpu.c
> +++ b/hw/acpi/cpu.c
> @@ -341,6 +341,7 @@ const VMStateDescription vmstate_cpu_hotplug = {
>   #define CPU_INSERT_EVENT  "CINS"
>   #define CPU_REMOVE_EVENT  "CRMV"
>   #define CPU_EJECT_EVENT   "CEJ0"
> +#define CPU_FW_EJECT_EVENT "CEJF"
>   
>   void build_cpus_aml(Aml *table, MachineState *machine, CPUHotplugFeatures opts,
>                       hwaddr io_base,
> @@ -393,7 +394,10 @@ void build_cpus_aml(Aml *table, MachineState *machine, 
> CPUHotplugFeatures opts,
>           aml_append(field, aml_named_field(CPU_REMOVE_EVENT, 1));

  Bit 2: Device remove event, used to distinguish device for which
        no device eject request to OSPM was issued. Firmware must
        ignore this bit.

>           /* initiates device eject, write only */
>           aml_append(field, aml_named_field(CPU_EJECT_EVENT, 1));

  Bit 3: reserved and should be ignored by OSPM

> -        aml_append(field, aml_reserved_field(4));
> +        aml_append(field, aml_reserved_field(1));
> +        /* tell firmware to do device eject, write only */
> +        aml_append(field, aml_named_field(CPU_FW_EJECT_EVENT, 1));
> +        aml_append(field, aml_reserved_field(2));

Shouldn't this be instead:

> -        aml_append(field, aml_reserved_field(4));
> +        /* tell firmware to do device eject, write only */
> +        aml_append(field, aml_named_field(CPU_FW_EJECT_EVENT, 1));
> +        aml_append(field, aml_reserved_field(3));

  Bit 4: if set to 1, OSPM requests firmware to perform device eject.
  Bit 5-7: reserved and should be ignored by OSPM

Otherwise AFAICS CPU_FW_EJECT_EVENT would correspond to bit 5.


Ankur

>           aml_append(field, aml_named_field(CPU_COMMAND, 8));
>           aml_append(cpu_ctrl_dev, field);
>   
> @@ -428,6 +432,7 @@ void build_cpus_aml(Aml *table, MachineState *machine, CPUHotplugFeatures opts,
>           Aml *ins_evt = aml_name("%s.%s", cphp_res_path, CPU_INSERT_EVENT);
>           Aml *rm_evt = aml_name("%s.%s", cphp_res_path, CPU_REMOVE_EVENT);
>           Aml *ej_evt = aml_name("%s.%s", cphp_res_path, CPU_EJECT_EVENT);
> +        Aml *fw_ej_evt = aml_name("%s.%s", cphp_res_path, CPU_FW_EJECT_EVENT);
>   
>           aml_append(cpus_dev, aml_name_decl("_HID", aml_string("ACPI0010")));
>           aml_append(cpus_dev, aml_name_decl("_CID", aml_eisaid("PNP0A05")));
> @@ -470,7 +475,13 @@ void build_cpus_aml(Aml *table, MachineState *machine, 
> CPUHotplugFeatures opts,
>   
>               aml_append(method, aml_acquire(ctrl_lock, 0xFFFF));
>               aml_append(method, aml_store(idx, cpu_selector));
> -            aml_append(method, aml_store(one, ej_evt));
> +            if (opts.fw_unplugs_cpu) {
> +                aml_append(method, aml_store(one, fw_ej_evt));
> +                aml_append(method, aml_store(aml_int(OVMF_CPUHP_SMI_CMD),
> +                           aml_name("%s", opts.smi_path)));
> +            } else {
> +                aml_append(method, aml_store(one, ej_evt));
> +            }
>               aml_append(method, aml_release(ctrl_lock));
>           }
>           aml_append(cpus_dev, method);
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index 9036e5594c..475e76f514 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -1586,6 +1586,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
>           CPUHotplugFeatures opts = {
>               .acpi_1_compatible = true, .has_legacy_cphp = true,
>               .smi_path = pm->smi_on_cpuhp ? "\\_SB.PCI0.SMI0.SMIC" : NULL,
> +            .fw_unplugs_cpu = pm->smi_on_cpu_unplug,
>           };
>           build_cpus_aml(dsdt, machine, opts, pm->cpu_hp_io_base,
>                          "\\_SB.PCI0", "\\_GPE._E02");