On 11/26/20 11:24, Ankur Arora wrote:
> On 2020-11-24 4:25 a.m., Igor Mammedov wrote:
>> If firmware negotiates ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT feature,
>> OSPM on CPU eject will set bit #4 in CPU hotplug block for to be
>> ejected CPU to mark it for removal by firmware and trigger SMI
>> upcall to let firmware do actual eject.
>>
>> Signed-off-by: Igor Mammedov <imamm...@redhat.com>
>> ---
>> PS:
>> - abuse 5.1 machine type for now to turn off unplug feature
>> (it will be moved to 5.2 machine type once new merge window is open)
>> ---
>> include/hw/acpi/cpu.h | 2 ++
>> docs/specs/acpi_cpu_hotplug.txt | 11 +++++++++--
>> hw/acpi/cpu.c | 18 ++++++++++++++++--
>> hw/i386/acpi-build.c | 5 +++++
>> hw/i386/pc.c | 1 +
>> hw/isa/lpc_ich9.c | 2 +-
>> 6 files changed, 34 insertions(+), 5 deletions(-)
>>
>> diff --git a/include/hw/acpi/cpu.h b/include/hw/acpi/cpu.h
>> index 0eeedaa491..999caaf510 100644
>> --- a/include/hw/acpi/cpu.h
>> +++ b/include/hw/acpi/cpu.h
>> @@ -22,6 +22,7 @@ typedef struct AcpiCpuStatus {
>> uint64_t arch_id;
>> bool is_inserting;
>> bool is_removing;
>> + bool fw_remove;
>> uint32_t ost_event;
>> uint32_t ost_status;
>> } AcpiCpuStatus;
>> @@ -50,6 +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/docs/specs/acpi_cpu_hotplug.txt
>> b/docs/specs/acpi_cpu_hotplug.txt
>> index 9bb22d1270..f68ef6e06c 100644
>> --- a/docs/specs/acpi_cpu_hotplug.txt
>> +++ b/docs/specs/acpi_cpu_hotplug.txt
>> @@ -57,7 +57,11 @@ read access:
>> It's valid only when bit 0 is set.
>> 2: Device remove event, used to distinguish device for which
>> no device eject request to OSPM was issued.
>> - 3-7: reserved and should be ignored by OSPM
>> + 3: reserved and should be ignored by OSPM
>> + 4: if set to 1, OSPM requests firmware to perform device
>> eject,
>> + firmware shall clear this event by writing 1 into it
>> before
>> + performing device eject> + 5-7: reserved and
>> should be ignored by OSPM
>> [0x5-0x7] reserved
>> [0x8] Command data: (DWORD access)
>> contains 0 unless value last stored in 'Command field' is
>> one of:
>> @@ -82,7 +86,10 @@ write access:
>> selected CPU device
>> 3: if set to 1 initiates device eject, set by OSPM when it
>> triggers CPU device removal and calls _EJ0 method
>> - 4-7: reserved, OSPM must clear them before writing to
>> register
>> + 4: if set to 1 OSPM hands over device eject to firmware,
>> + Firmware shall issue device eject request as described
>> above
>> + (bit #3) and OSPM should not touch device eject bit (#3),
>> + 5-7: reserved, OSPM must clear them before writing to
>> register
>> [0x5] Command field: (1 byte access)
>> value:
>> 0: selects a CPU device with inserting/removing events and
>> diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c
>> index f099b50927..09d2f20dae 100644
>> --- a/hw/acpi/cpu.c
>> +++ b/hw/acpi/cpu.c
>> @@ -71,6 +71,7 @@ static uint64_t cpu_hotplug_rd(void *opaque, hwaddr
>> addr, unsigned size)
>> val |= cdev->cpu ? 1 : 0;
>> val |= cdev->is_inserting ? 2 : 0;
>> val |= cdev->is_removing ? 4 : 0;
>> + val |= cdev->fw_remove ? 16 : 0;
>
> I might be missing something but I don't see where cdev->fw_remove is being
> set.
See just below, in the cpu_hotplug_wr() hunk. When bit#4 is written --
which happens through the ACPI code change --, fw_remove is inverted.
> We do set cdev->is_removing in acpi_cpu_unplug_request_cb() so AFAICS
> we would always end up setting this bit:
>> val |= cdev->is_removing ? 4 : 0;
>
> Also, if cdev->fw_remove and cdev->is_removing are both true, val would be
> (4 | 16). I'm guessing that in that case the AML determines which case gets
> handled but it might make sense to set just one of these?
"is_removing" is set directly in response to the device_del QMP command.
That QMP command is asynchronous to the execution of the guest OS.
"fw_remove" is set (by virtue of inverting) by ACPI CEJ0, which is
executed by the guest OS's ACPI interpreter, after the guest OS has
de-scheduled all processes from the CPU being removed (= basically after
the OS has willfully forgotten about the CPU).
Therefore, considering the bitmask (is_removing, fw_remove), three
variations make sense:
#1 (is_removing=0, fw_remove=0) -- normal status; no unplug requested
#2 (is_removing=1, fw_remove=0) -- unplug requested via QMP, guest OS
is processing the request
#3 (is_removing=1, fw_remove=1) -- guest OS removed all references from
the CPU, firmware is permitted /
required to forget about the CPU as
well, and then unplug the CPU
#4 (is_removing=1, fw_remove=0) -- fimware is about to unplug the CPU
#5 (is_removing=0, fw_remove=0) -- firmware performing unplug
The variation (is_removing=0, fw_remove=1) is invalid / unused.
The firmware may be investigating the CPU register block between steps
#2 and #3 -- in other words, the firmware may see a CPU for which
is_remove is set (unplug requested via QMP), but the OS has not vacated
yet (fw_remove=0). In that case, the firmware must just skip the CPU --
once the OS is done, it will set fw_remove too, and raise another SMI.
>
>
>> trace_cpuhp_acpi_read_flags(cpu_st->selector, val);
>> break;
>> case ACPI_CPU_CMD_DATA_OFFSET_RW:
>> @@ -148,6 +149,8 @@ static void cpu_hotplug_wr(void *opaque, hwaddr
>> addr, uint64_t data,
>> hotplug_ctrl = qdev_get_hotplug_handler(dev);
>> hotplug_handler_unplug(hotplug_ctrl, dev, NULL);
>> object_unparent(OBJECT(dev));
>> + } else if (data & 16) {
>> + cdev->fw_remove = !cdev->fw_remove;
>> }
>> break;
>> case ACPI_CPU_CMD_OFFSET_WR:
>> @@ -332,6 +335,7 @@ 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,
>> @@ -384,7 +388,10 @@ void build_cpus_aml(Aml *table, MachineState
>> *machine, CPUHotplugFeatures opts,
>> aml_append(field, aml_named_field(CPU_REMOVE_EVENT, 1));
>> /* initiates device eject, write only */
>> aml_append(field, aml_named_field(CPU_EJECT_EVENT, 1));
>> - 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));
>> aml_append(field, aml_named_field(CPU_COMMAND, 8));
>> aml_append(cpu_ctrl_dev, field);
>> @@ -419,6 +426,7 @@ 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")));
>> @@ -461,7 +469,13 @@ 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));
>> + }
> My knowledge of AML is rather rudimentary but this looks mostly
> reasonable to me.
>
> One question: the corresponding code for CPU hotplug does not send an
> SMI_CMD.
> Why the difference?
This code (on eject) is executing *after* the OS kernel has processed
the event. But on hotplug, the ordering is different (it must be): in
that case, the CSCN (scan) method first notifies the firmware, and then
the OS.
Thanks
Laszlo
>
> aml_append(while_ctx,
> aml_store(aml_derefof(aml_index(new_cpus,
> cpu_idx)),
> uid));
> aml_append(while_ctx,
> aml_call2(CPU_NOTIFY_METHOD, uid, dev_chk));
> aml_append(while_ctx, aml_store(uid, cpu_selector));
> aml_append(while_ctx, aml_store(one, ins_evt));
> aml_append(while_ctx, aml_increment(cpu_idx));
>
>
>> 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 1f5c211245..475e76f514 100644
>> --- a/hw/i386/acpi-build.c
>> +++ b/hw/i386/acpi-build.c
>> @@ -96,6 +96,7 @@ typedef struct AcpiPmInfo {
>> bool s4_disabled;
>> bool pcihp_bridge_en;
>> bool smi_on_cpuhp;
>> + bool smi_on_cpu_unplug;
>> bool pcihp_root_en;
>> uint8_t s4_val;
>> AcpiFadtData fadt;
>> @@ -197,6 +198,7 @@ static void acpi_get_pm_info(MachineState
>> *machine, AcpiPmInfo *pm)
>> pm->pcihp_io_base = 0;
>> pm->pcihp_io_len = 0;
>> pm->smi_on_cpuhp = false;
>> + pm->smi_on_cpu_unplug = false;
>> assert(obj);
>> init_common_fadt_data(machine, obj, &pm->fadt);
>> @@ -220,6 +222,8 @@ static void acpi_get_pm_info(MachineState
>> *machine, AcpiPmInfo *pm)
>> pm->cpu_hp_io_base = ICH9_CPU_HOTPLUG_IO_BASE;
>> pm->smi_on_cpuhp =
>> !!(smi_features & BIT_ULL(ICH9_LPC_SMI_F_CPU_HOTPLUG_BIT));
>> + pm->smi_on_cpu_unplug =
>> + !!(smi_features &
>> BIT_ULL(ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT));
>> }
>> /* The above need not be conditional on machine type because
>> the reset port
>> @@ -1582,6 +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");
>> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
>> index 17b514d1da..2952a00fe6 100644
>> --- a/hw/i386/pc.c
>> +++ b/hw/i386/pc.c
>> @@ -99,6 +99,7 @@
>> GlobalProperty pc_compat_5_1[] = {
>> { "ICH9-LPC", "x-smi-cpu-hotplug", "off" },
>> + { "ICH9-LPC", "x-smi-cpu-hotunplug", "off" },
>> };
>> const size_t pc_compat_5_1_len = G_N_ELEMENTS(pc_compat_5_1);
>> diff --git a/hw/isa/lpc_ich9.c b/hw/isa/lpc_ich9.c
>> index 087a18d04d..8c667b7166 100644
>> --- a/hw/isa/lpc_ich9.c
>> +++ b/hw/isa/lpc_ich9.c
>> @@ -770,7 +770,7 @@ static Property ich9_lpc_properties[] = {
>> DEFINE_PROP_BIT64("x-smi-cpu-hotplug", ICH9LPCState,
>> smi_host_features,
>> ICH9_LPC_SMI_F_CPU_HOTPLUG_BIT, true),
>> DEFINE_PROP_BIT64("x-smi-cpu-hotunplug", ICH9LPCState,
>> smi_host_features,
>> - ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT, false),
>> + ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT, true),
>> DEFINE_PROP_END_OF_LIST(),
>> };
>>
>
> Thanks for sending out the patch btw. This helped me crystallize some of
> the
> corresponding OVMF code.
>
> Ankur
>
