Re: [PATCH v4 3/4] liveupdate: luo_session: include linux/mm.h for virt/phys translation

[Pratyush Yadav <pratyush@kernel.org>]

On Mon, Aug 10 2026, Pratyush Yadav wrote:

> On Mon, Aug 10 2026, Huacai Chen wrote:
>
>> Hi, George,
>>
>> This should be the 2nd patch.
>
> Agreed.
>
> With that done,
>
> Reviewed-by: Pratyush Yadav <pratyush@kernel.org>

Actually, I take this back. Sashiko has found some problems. See below.

>
>>
>> Huacai
>>
>> On Fri, Aug 7, 2026 at 6:39 PM George Guo <dongtai.guo@linux.dev> wrote:
>>>
>>> From: George Guo <guodongtai@kylinos.cn>
>>>
>>> luo_session.c calls virt_to_phys() and phys_to_virt(). On LoongArch with
>>> CONFIG_KFENCE=y, these macros (in arch/loongarch/include/asm/io.h) expand
>>> to offset_in_page() and page_address(), both declared in <linux/mm.h>.

https://sashiko.dev/#/patchset/20260807103714.33074-5-dongtai.guo@linux.dev

    Is this description accurate? Looking at luo_session.c, it does not actually
    call virt_to_phys().
    The implicit declaration error appears to originate from arch_kfence_init_pool()
    in arch/loongarch/include/asm/kfence.h, which is implicitly included via
    <linux/slab.h>.
    arch/loongarch/include/asm/kfence.h:arch_kfence_init_pool() {
        ...
                    virt_to_phys((void *)kfence_pool), PAGE_KERNEL);
        ...
    }
    Could the fix be applied to the architecture header instead, to prevent any
    other kernel C file on LoongArch with CONFIG_KFENCE=y from suffering the same
    build failure if it includes <linux/slab.h> before <linux/mm.h>?

I at least don't see any virt_to_phys() or phys_to_virt() in
luo_session.c. So you need to go and take another look at what the real
problem is and what the fix should be.

>>>
>>> Since luo_session.c only includes <linux/io.h>, the translation unit fails
>>> to build with CONFIG_KFENCE=y:
>>>
>>>   asm/io.h: error: implicit declaration of function 'offset_in_page'
>>>   asm/io.h: error: implicit declaration of function 'page_address'
>>>
>>> Add the missing include to fix these build errors.
>>>
>>> Co-developed-by: Kexin Liu <liukexin@kylinos.cn>
>>> Signed-off-by: Kexin Liu <liukexin@kylinos.cn>
>>> Signed-off-by: George Guo <guodongtai@kylinos.cn>
>>> Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
>>> ---
>>>  kernel/liveupdate/luo_session.c | 1 +
>>>  1 file changed, 1 insertion(+)
>>>
>>> diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c
>>> index f38b5b18f3f8..31490ac7b63d 100644
>>> --- a/kernel/liveupdate/luo_session.c
>>> +++ b/kernel/liveupdate/luo_session.c
>>> @@ -94,6 +94,7 @@
>>>  #include <linux/kho/abi/luo.h>
>>>  #include <linux/list.h>
>>>  #include <linux/liveupdate.h>
>>> +#include <linux/mm.h>
>>>  #include <linux/mutex.h>
>>>  #include <linux/rwsem.h>
>>>  #include <linux/slab.h>
>>> --
>>> 2.53.0
>>>
>>>

-- 
Regards,
Pratyush Yadav