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

[Auger Eric]

Hi Shameer,

On 3/29/19 10:59 AM, Shameerali Kolothum Thodi wrote:
> 
> 
>> -----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.
>>
>>>
>>> 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.
>>>
>>> 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.
> 
> Sorry I missed this part. Yes, that will be a more cleaner solution.
> 
> Also, to be more clear on what happens,
> 
> Guest ACPI boot with "fdt=on" ,
> 
> From kernel log,
> 
> [    0.000000] Early memory node ranges
> [    0.000000]   node   0: [mem 0x0000000040000000-0x00000000bbf5ffff]
> [    0.000000]   node   0: [mem 0x00000000bbf60000-0x00000000bbffffff]
> [    0.000000]   node   0: [mem 0x00000000bc000000-0x00000000bc02ffff]
> [    0.000000]   node   0: [mem 0x00000000bc030000-0x00000000bc36ffff]
> [    0.000000]   node   0: [mem 0x00000000bc370000-0x00000000bf64ffff]
> [    0.000000]   node   0: [mem 0x00000000bf650000-0x00000000bf6dffff]
> [    0.000000]   node   0: [mem 0x00000000bf6e0000-0x00000000bf6effff]
> [    0.000000]   node   0: [mem 0x00000000bf6f0000-0x00000000bf80ffff]
> [    0.000000]   node   0: [mem 0x00000000bf810000-0x00000000bfffffff]
> [    0.000000]   node   0: [mem 0x00000000c0000000-0x00000000ffffffff]  --> 
> This is the hotpluggable memory node from DT.
> [    0.000000] Zeroed struct page in unavailable ranges: 1040 pages
> [    0.000000] Initmem setup node 0 [mem 
> 0x0000000040000000-0x00000000ffffffff]
> 
> 
> Guest ACPI boot with "fdt=off" ,
> 
> [    0.000000] Movable zone start for each node
> [    0.000000] Early memory node ranges
> [    0.000000]   node   0: [mem 0x0000000040000000-0x00000000bbf5ffff]
> [    0.000000]   node   0: [mem 0x00000000bbf60000-0x00000000bbffffff]
> [    0.000000]   node   0: [mem 0x00000000bc000000-0x00000000bc02ffff]
> [    0.000000]   node   0: [mem 0x00000000bc030000-0x00000000bc36ffff]
> [    0.000000]   node   0: [mem 0x00000000bc370000-0x00000000bf64ffff]
> [    0.000000]   node   0: [mem 0x00000000bf650000-0x00000000bf6dffff]
> [    0.000000]   node   0: [mem 0x00000000bf6e0000-0x00000000bf6effff]
> [    0.000000]   node   0: [mem 0x00000000bf6f0000-0x00000000bf80ffff]
> [    0.000000]   node   0: [mem 0x00000000bf810000-0x00000000bfffffff]
> [    0.000000] Zeroed struct page in unavailable ranges: 1040 pages
> [    0.000000] Initmem setup node 0 [mem 0x0000000040000000-0x00000000bfffffff
> 
> The hotpluggable memory node is absent from early memory nodes here.

OK thank you for the example illustrating the concern.
> 
> As you said, it could be possible to detect this node using SRAT in UEFI.

Let's wait for EDK2 experts on this.

Thanks

Eric
> 
> Cheers,
> Shameer
> 
>>> 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;
>>>