Re: [PATCH v2 1/7] x86: lpc9: let firmware negotiate 'CPU hotplug with SMI' features

[Laszlo Ersek]

correcting myself a bit, with Drew and Thomas CC'd as well:

On 08/19/20 10:39, Laszlo Ersek wrote:
> Hi Igor,
> 
> (CC'ing Daniel, Cornelia, David, Peter)
> 
> On 08/18/20 14:22, Igor Mammedov wrote:
>> It will allow firmware to notify QEMU that firmware requires SMI
>> being triggered on CPU hot[un]plug, so that it would be able to account
>> for hotplugged CPU and relocate it to new SMM base and/or safely remove
>> CPU on unplug.
>>
>> Using negotiated features, follow up patches will insert SMI upcall
>> into AML code, to make sure that firmware processes hotplug before
>> guest OS would attempt to use new CPU.
>>
>> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
>> Reviewed-by: Laszlo Ersek <lersek@redhat.com>
>> ---
>> v2:
>>   - rebase on top of 5.1 (move compat values to 5.1 machine)
>>   - make "x-smi-cpu-hotunplug" false by default (Laszlo Ersek 
>> <lersek@redhat.com>)
>> ---
>>  include/hw/i386/ich9.h |  2 ++
>>  include/hw/i386/pc.h   |  3 +++
>>  hw/i386/pc.c           |  6 +++++-
>>  hw/i386/pc_piix.c      |  1 +
>>  hw/i386/pc_q35.c       |  1 +
>>  hw/isa/lpc_ich9.c      | 13 +++++++++++++
>>  6 files changed, 25 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/hw/i386/ich9.h b/include/hw/i386/ich9.h
>> index a98d10b252..d1bb3f7bf0 100644
>> --- a/include/hw/i386/ich9.h
>> +++ b/include/hw/i386/ich9.h
>> @@ -247,5 +247,7 @@ typedef struct ICH9LPCState {
>>
>>  /* bit positions used in fw_cfg SMI feature negotiation */
>>  #define ICH9_LPC_SMI_F_BROADCAST_BIT            0
>> +#define ICH9_LPC_SMI_F_CPU_HOTPLUG_BIT          1
>> +#define ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT       2
>>
>>  #endif /* HW_ICH9_H */
>> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
>> index 3d7ed3a55e..fe52e165b2 100644
>> --- a/include/hw/i386/pc.h
>> +++ b/include/hw/i386/pc.h
>> @@ -193,6 +193,9 @@ void pc_system_firmware_init(PCMachineState *pcms, 
>> MemoryRegion *rom_memory);
>>  void pc_madt_cpu_entry(AcpiDeviceIf *adev, int uid,
>>                         const CPUArchIdList *apic_ids, GArray *entry);
>>
>> +extern GlobalProperty pc_compat_5_1[];
>> +extern const size_t pc_compat_5_1_len;
>> +
>>  extern GlobalProperty pc_compat_5_0[];
>>  extern const size_t pc_compat_5_0_len;
>>
>> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
>> index 47c5ca3e34..99c6bdbab4 100644
>> --- a/hw/i386/pc.c
>> +++ b/hw/i386/pc.c
>> @@ -97,8 +97,12 @@
>>  #include "fw_cfg.h"
>>  #include "trace.h"
>>
>> -GlobalProperty pc_compat_5_0[] = {
>> +GlobalProperty pc_compat_5_1[] = {
>> +    { "ICH9-LPC", "x-smi-cpu-hotplug", "off" },
>>  };
>> +const size_t pc_compat_5_1_len = G_N_ELEMENTS(pc_compat_5_1);
>> +
>> +GlobalProperty pc_compat_5_0[] = { };
>>  const size_t pc_compat_5_0_len = G_N_ELEMENTS(pc_compat_5_0);
>>
>>  GlobalProperty pc_compat_4_2[] = {
>> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
>> index b789e83f9a..d56f2e1b96 100644
>> --- a/hw/i386/pc_piix.c
>> +++ b/hw/i386/pc_piix.c
>> @@ -433,6 +433,7 @@ static void pc_i440fx_5_1_machine_options(MachineClass 
>> *m)
>>      m->alias = "pc";
>>      m->is_default = true;
>>      pcmc->default_cpu_version = 1;
>> +    compat_props_add(m->compat_props, pc_compat_5_1, pc_compat_5_1_len);
>>  }
>>
>>  DEFINE_I440FX_MACHINE(v5_1, "pc-i440fx-5.1", NULL,
>> diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
>> index a3e607a544..0ca1146a59 100644
>> --- a/hw/i386/pc_q35.c
>> +++ b/hw/i386/pc_q35.c
>> @@ -359,6 +359,7 @@ static void pc_q35_5_1_machine_options(MachineClass *m)
>>      pc_q35_machine_options(m);
>>      m->alias = "q35";
>>      pcmc->default_cpu_version = 1;
>> +    compat_props_add(m->compat_props, pc_compat_5_1, pc_compat_5_1_len);
>>  }
>>
>>  DEFINE_Q35_MACHINE(v5_1, "pc-q35-5.1", NULL,
>> diff --git a/hw/isa/lpc_ich9.c b/hw/isa/lpc_ich9.c
>> index cd6e169d47..19f32bed3e 100644
>> --- a/hw/isa/lpc_ich9.c
>> +++ b/hw/isa/lpc_ich9.c
>> @@ -373,6 +373,15 @@ static void smi_features_ok_callback(void *opaque)
>>          /* guest requests invalid features, leave @features_ok at zero */
>>          return;
>>      }
>> +    if (!(guest_features & BIT_ULL(ICH9_LPC_SMI_F_BROADCAST_BIT)) &&
>> +        guest_features & (BIT_ULL(ICH9_LPC_SMI_F_CPU_HOTPLUG_BIT) |
>> +                          BIT_ULL(ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT))) {
>> +        /*
>> +         * cpu hot-[un]plug with SMI requires SMI broadcast,
>> +         * leave @features_ok at zero
>> +         */
>> +        return;
>> +    }
>>
>>      /* valid feature subset requested, lock it down, report success */
>>      lpc->smi_negotiated_features = guest_features;
>> @@ -747,6 +756,10 @@ static Property ich9_lpc_properties[] = {
>>      DEFINE_PROP_BOOL("noreboot", ICH9LPCState, pin_strap.spkr_hi, true),
>>      DEFINE_PROP_BIT64("x-smi-broadcast", ICH9LPCState, smi_host_features,
>>                        ICH9_LPC_SMI_F_BROADCAST_BIT, true),
>> +    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),
>>      DEFINE_PROP_END_OF_LIST(),
>>  };
>>
>>
> 
> this patch does the right thing for the 5.1 PC machine types, but it
> does not introduce any 5.2 machine types, so I can't enable the hotplug
> feature bit without messing with the x-smi-cpu-hotplug property
> manually.
> 
> Now... looking at the mailing list, I can see the following patch
> pending review (posted by Daniel ~5 days ago):
> 
>   [PATCH 01/10] hw: add compat machines for 5.2
>   20200814205424.543857-2-danielhb413@gmail.com">http://mid.mail-archive.com/20200814205424.543857-2-danielhb413@gmail.com
> 
> That patch introduces the 5.2 PC machine types.
> 
> However, I can't just apply your series on top of that one patch,
> because they conflict at least on the "pc_compat_5_1" array.
> 
> Given that Daniel's patch was posted before yours, and also that
> Daniel's patch introduces 5.2 machine types for arm, ppc and s390x too
> (and the "hw_compat_5_1" array in addition to the "pc_compat_5_1"
> array), I'd like to request:
> 
> - that we please review and/or merge Daniel's patch in isolation (just
>   the first patch in the containing series, not the entire series!),
> 
> - and that you please rebase your series on top of Daniel's patch.
> 
> If Daniel's patch is approved as-is on the list, then I'm OK applying it
> locally in isolation from the rest of the containing series, as a basis
> for locally applying your v3.
> 
> (I could resolve the conflicts myself at once I guess, and proceed with
> the review / testing -- but that's not really useful if I want to give a
> formal Tested-by. I wouldn't be testing the patches as they were
> posted.)

Sorry, I've just realized: the patch in question was originally written
by Cornelia. And it's been on the list for a good time now -- it's been
multiply reviewed, and also picked up in other series several times:

Original posting, with reviews:

http://mid.mail-archive.com/20200728094645.272149-1-cohuck@redhat.com

Picked into another series (different from Daniel's):

20200805091640.11134-2-drjones@redhat.com">http://mid.mail-archive.com/20200805091640.11134-2-drjones@redhat.com

Peter, would you please consider pushing that one patch directly? It
seems to be a choke point.

Thanks!
Laszlo