linux-kernel - Re: [PATCH -V2] tdx, memory hotplug: Check whole hot-adding memory range for TDX

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Message-ID: <87v7xz81jk.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date: Fri, 11 Oct 2024 16:51:59 +0800
From: "Huang, Ying" <ying.huang@...el.com>
To: David Hildenbrand <david@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,  Ingo Molnar <mingo@...hat.com>,
  Borislav Petkov <bp@...en8.de>,  Dave Hansen
 <dave.hansen@...ux.intel.com>,  "Kirill A . Shutemov"
 <kirill.shutemov@...ux.intel.com>,  x86@...nel.org,
  linux-coco@...ts.linux.dev,  linux-mm@...ck.org,
  linux-kernel@...r.kernel.org,  Dan Williams <dan.j.williams@...el.com>,
  Kai Huang <kai.huang@...el.com>,  "H. Peter Anvin" <hpa@...or.com>,  Andy
 Lutomirski <luto@...nel.org>,  Oscar Salvador <osalvador@...e.de>
Subject: Re: [PATCH -V2] tdx, memory hotplug: Check whole hot-adding memory
 range for TDX

David Hildenbrand <david@...hat.com> writes:

> On 11.10.24 03:27, Huang, Ying wrote:
>> David Hildenbrand <david@...hat.com> writes:
>> 
>>>>    extern u64 max_mem_size;
>>>>      extern int mhp_online_type_from_str(const char *str);
>>>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>>>> index 621ae1015106..c4769f24b1e2 100644
>>>> --- a/mm/memory_hotplug.c
>>>> +++ b/mm/memory_hotplug.c
>>>> @@ -1305,6 +1305,11 @@ int try_online_node(int nid)
>>>>    	return ret;
>>>>    }
>>>>    +int __weak arch_check_hotplug_memory_range(u64 start, u64 size)
>>>> +{
>>>> +	return 0;
>>>> +}
>>>
>>> BTW, I remember that "__weak" doesn't always behave the way it would
>>> seem, which is the reason we're usually using
>>>
>>> #define arch_check_hotplug_memory_range arch_check_hotplug_memory_range
>>>
>>> #ifndef arch_check_hotplug_memory_range
>>> ...
>>> #endif
>>>
>>>
>>> Not that I remember the details, just that it can result in rather
>>> surprising outcomes (e.g., the wrong function getting called).
>> I can replace __weak with #define/#ifndef.
>> However, it appears that "__weak" is still widely used now.
>
> Probably better to avoid new ones.

Sure.  Will do that in the future versions.

> See also
> Documentation/dev-tools/checkpatch.rst
>
> I assume checkpatch.pl should complain as well?

Double checked again.  It doesn't complain for that.

--
Best Regards,
Huang, Ying