Re: [Qemu-devel] [PATCH v3 07/10] hw/arm/virt: Introduce opt-in feature "fdt"

[Auger Eric]

Hi Shameer,
On 3/29/19 10:41 AM, Shameerali Kolothum Thodi wrote:
> Hi Eric,
> 
>> -----Original Message-----
>> From: Auger Eric [mailto:address@hidden
>> Sent: 29 March 2019 09:32
>> To: Shameerali Kolothum Thodi <address@hidden>;
>> address@hidden; address@hidden; address@hidden;
>> address@hidden; address@hidden;
>> address@hidden; address@hidden
>> Cc: Linuxarm <address@hidden>; xuwei (O) <address@hidden>;
>> Laszlo Ersek <address@hidden>; Ard Biesheuvel
>> <address@hidden>; Leif Lindholm <address@hidden>
>> Subject: Re: [PATCH v3 07/10] hw/arm/virt: Introduce opt-in feature "fdt"
>>
>> Hi Shameer,
>>
>> [ + Laszlo, Ard, Leif ]
>>
>> On 3/21/19 11:47 AM, Shameer Kolothum wrote:
>>> This is to disable/enable populating DT nodes in case
>>> any conflict with acpi tables. The default is "off".
>> The name of the option sounds misleading to me. Also we don't really
>> know the scope of the disablement. At the moment this just aims to
>> prevent the hotpluggable dt nodes from being added if we boot in ACPI mode.
> 
> Yes, I was not very happy with the name "fdt". If this is not useful other 
> than
> this device memory conflict case, then we can be more specific. But I am not 
> sure
> we might need this for any other future conflicts, hence a more generic name. 
> 
> May be "force_fdt" or "dimm_fdt"? I am open to suggestions.
mask_spurious_dt_nodes. But I am unsure this is the way we should go.
> 
>>>
>>> This will be used in subsequent patch where cold plug
>>> device-memory support is added for DT boot.
>> I am concerned about the fact that in dt mode, by default, you won't see
>> any PCDIMM nodes.
> 
> True. But is there any other way to detect that the Guest is using DT?
I don't know any

in machvirt_init, there is firmware_loaded that tells you whether you
have a FW image. If this one is not set, you can induce dt. But if there
is a FW it can be either DT or ACPI booted. You also have the
acpi_enabled knob.

Thanks

Eric
> 
> Thanks,
> Shameer
> 
>>> If DT memory node support is added for cold-plugged device
>>> memory, those memory will be visible to Guest kernel via
>>> UEFI GetMemoryMap() and gets treated as early boot memory.
>> Don't we have an issue in UEFI then. Normally the SRAT indicates whether
>> the slots are hotpluggable or not. Shouldn't the UEFI code look at this
>> info.
>>> Hence memory becomes non hot-un-unpluggable even if Guest
>>> is booted in ACPI mode.
>>
>>
>>
>>>
>>> Signed-off-by: Shameer Kolothum <address@hidden>
>>> ---
>>>  hw/arm/virt.c         | 23 +++++++++++++++++++++++
>>>  include/hw/arm/virt.h |  1 +
>>>  2 files changed, 24 insertions(+)
>>>
>>> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
>>> index 13db0e9..b602151 100644
>>> --- a/hw/arm/virt.c
>>> +++ b/hw/arm/virt.c
>>> @@ -1717,6 +1717,20 @@ static void virt_set_highmem(Object *obj, bool
>> value, Error **errp)
>>>      vms->highmem = value;
>>>  }
>>>
>>> +static bool virt_get_fdt(Object *obj, Error **errp)
>>> +{
>>> +    VirtMachineState *vms = VIRT_MACHINE(obj);
>>> +
>>> +    return vms->use_fdt;
>>> +}
>>> +
>>> +static void virt_set_fdt(Object *obj, bool value, Error **errp)
>>> +{
>>> +    VirtMachineState *vms = VIRT_MACHINE(obj);
>>> +
>>> +    vms->use_fdt = value;
>>> +}
>>> +
>>>  static bool virt_get_its(Object *obj, Error **errp)
>>>  {
>>>      VirtMachineState *vms = VIRT_MACHINE(obj);
>>> @@ -2005,6 +2019,15 @@ static void virt_instance_init(Object *obj)
>>>      object_property_set_description(obj, "gic-version",
>>>                                      "Set GIC version. "
>>>                                      "Valid values are 2, 3 and host",
>> NULL);
>>> +    /* fdt is disabled by default */
>>> +    vms->use_fdt = false;
>>> +    object_property_add_bool(obj, "fdt", virt_get_fdt,
>>> +                             virt_set_fdt, NULL);
>>> +    object_property_set_description(obj, "fdt",
>>> +                                    "Set on/off to enable/disable
>> device tree "
>>> +                                    "nodes in case any conflict with
>> ACPI"
>> in case of
>>
>> Thanks
>>
>> Eric
>>> +                                    "(eg: device memory node)",
>>> +                                    NULL);
>>>
>>>      vms->highmem_ecam = !vmc->no_highmem_ecam;
>>>
>>> diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
>>> index c5e4c96..14b2e0a 100644
>>> --- a/include/hw/arm/virt.h
>>> +++ b/include/hw/arm/virt.h
>>> @@ -119,6 +119,7 @@ typedef struct {
>>>      bool highmem_ecam;
>>>      bool its;
>>>      bool virt;
>>> +    bool use_fdt;
>>>      int32_t gic_version;
>>>      VirtIOMMUType iommu;
>>>      struct arm_boot_info bootinfo;
>>>