Re: [PATCH v7 5/6] tools: Allow building xen-hptool without CONFIG_MIGRATE

[Jan Beulich <jbeulich@xxxxxxxx>]

On 16.04.2026 10:22, Mykyta Poturai wrote:
> On 4/16/26 09:49, Jan Beulich wrote:
>> On 15.04.2026 16:51, Mykyta Poturai wrote:
>>> On 3/30/26 15:32, Jan Beulich wrote:
>>>> On 30.03.2026 13:59, Mykyta Poturai wrote:
>>>>> With CPU hotplug sysctls implemented on Arm it becomes useful to have a
>>>>> tool for calling them.
>>>>>
>>>>> According to the commit history it seems that putting hptool under
>>>>> config MIGRATE was a measure to fix IA64 build. As IA64 is no longer
>>>>> supported it can now be brought back. So build it unconditionally.
>>>>>
>>>>> Signed-off-by: Mykyta Poturai <mykyta_poturai@xxxxxxxx>
>>>>> ---
>>>>> v6->v7:
>>>>> * no changes
>>>>>
>>>>> v5->v6:
>>>>> * don't change order in Makefile
>>>>>
>>>>> v4->v5:
>>>>> * make hptool always build
>>>>>
>>>>> v3->v4:
>>>>> * no changes
>>>>>
>>>>> v2->v3:
>>>>> * no changes
>>>>>
>>>>> v1->v2:
>>>>> * switch to configure from legacy config
>>>>> ---
>>>>>    tools/libs/guest/Makefile.common | 2 +-
>>>>>    tools/misc/Makefile              | 2 +-
>>>>>    2 files changed, 2 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/tools/libs/guest/Makefile.common 
>>>>> b/tools/libs/guest/Makefile.common
>>>>> index b928a4a246..03dfcee7fa 100644
>>>>> --- a/tools/libs/guest/Makefile.common
>>>>> +++ b/tools/libs/guest/Makefile.common
>>>>> @@ -7,6 +7,7 @@ OBJS-y += xg_private.o
>>>>>    OBJS-y += xg_domain.o
>>>>>    OBJS-y += xg_suspend.o
>>>>>    OBJS-y += xg_resume.o
>>>>> +OBJS-y += xg_offline_page.o
>>>>>    ifeq ($(CONFIG_MIGRATE),y)
>>>>>    OBJS-y += xg_sr_common.o
>>>>>    OBJS-$(CONFIG_X86) += xg_sr_common_x86.o
>>>>> @@ -17,7 +18,6 @@ OBJS-$(CONFIG_X86) += xg_sr_save_x86_pv.o
>>>>>    OBJS-$(CONFIG_X86) += xg_sr_save_x86_hvm.o
>>>>>    OBJS-y += xg_sr_restore.o
>>>>>    OBJS-y += xg_sr_save.o
>>>>> -OBJS-y += xg_offline_page.o
>>>>>    else
>>>>>    OBJS-y += xg_nomigrate.o
>>>>>    endif
>>>>
>>>> This looks wrong to me. There are x86-specifics in that file, which 
>>>> shouldn't
>>>> be built on Arm. And the name of the file also doesn't indicate any 
>>>> relation
>>>> to CPU management.
>>>
>>> xen-hptool requires xg_offline_page as it has both CPU and memory
>>> hotplug commands. Without building xg_offline_page it fails with
>>>
>>> xen-hptool: symbol lookup error: xen-hptool: undefined symbol:
>>> xc_mark_page_offline, version libxenguest_4.22.0
>>>
>>> when trying to do memory ops.
>>>
>>> Is it an acceptable behavior?
>>
>> I don't think so, no. The tool wouldn't, aiui, load at all then if built with
>> "bindnow" enabled.
>>
>>> If so I guess we can build xg_offline page only on x86.
>>
>> We still need to, imo. But the tool still needs to be usable no matter how
>> specifically it is built. It should avoid referencing xg_offline_page.c
>> functions when built for non-x86.
> 
> As I understand, the usage of arch-specific compile time checks is 
> heavily discouraged in tools. So I don’t think it would be approved by 
> tools maintainers. Do we really need to omit this file if memory ops are 
> already getting blocked by Xen on Arm anyway?

Nothing I can answer in a way that's definitive for your purpose. As you
say, the final word here is with Anthony. I've voiced my opinion.

Jan