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Message-ID: <9f1d5ffe-840b-f332-559f-81899faf242c@bytedance.com>
Date:   Thu, 29 Sep 2022 16:42:55 +0800
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Subject: Re: [PATCH v2] mm: use update_mmu_tlb() on the second thread
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To:     =?UTF-8?B?6ZmI5Y2O5omN?= <chenhuacai@loongson.cn>,
        maobibo <maobibo@loongson.cn>
Cc:     Qi Zheng <zhengqi.arch@bytedance.com>,
        David Hildenbrand <david@redhat.com>,
        akpm@linux-foundation.org, muchun.song@linux.dev, chris@zankel.net,
        jcmvbkbc@gmail.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        Muchun Song <songmuchun@bytedance.com>
References: <20220926115621.13849-1-zhengqi.arch@bytedance.com>
 <b5823e18-6139-c16e-a2df-1aa3e88927fa@redhat.com>
 <c41a3cb6-aef9-d8a9-ab0b-b9c8013ee1d8@bytedance.com>
 <e5cd4c46-71fd-8edb-098c-2ac839d5c5d2@loongson.cn>
 <d4e4a362-fbf2-7eea-e021-16ae7782e06e@bytedance.com>
 <24f6df23-82cc-1290-e015-cba2a284e060@loongson.cn>
 <b702cc9.d17c.1838865fb5c.Coremail.chenhuacai@loongson.cn>
From:   Qi Zheng <zhengqi.arch@bytedance.com>
In-Reply-To: <b702cc9.d17c.1838865fb5c.Coremail.chenhuacai@loongson.cn>
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On 2022/9/29 16:38, 陈华才 wrote:
> Hi, all,
> 
> 
>> -----原始邮件-----
>> 发件人: maobibo <maobibo@loongson.cn>
>> 发送时间:2022-09-29 12:05:33 (星期四)
>> 收件人: "Qi Zheng" <zhengqi.arch@bytedance.com>, "David Hildenbrand" <david@redhat.com>, akpm@linux-foundation.org, muchun.song@linux.dev, "陈华才" <chenhuacai@loongson.cn>
>> 抄送: chris@zankel.net, jcmvbkbc@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Muchun Song" <songmuchun@bytedance.com>
>> 主题: Re: [PATCH v2] mm: use update_mmu_tlb() on the second thread
>>
>>
>>
>> 在 2022/9/29 11:47, Qi Zheng 写道:
>>>
>>>
>>> On 2022/9/29 11:27, maobibo wrote:
>>>> 在 2022/9/29 11:07, Qi Zheng 写道:
>>>>>
>>>>>
>>>>> On 2022/9/26 22:34, David Hildenbrand wrote:
>>>>>> On 26.09.22 13:56, Qi Zheng wrote:
>>>>>>> As message in commit 7df676974359 ("mm/memory.c: Update local TLB
>>>>>>> if PTE entry exists") said, we should update local TLB only on the
>>>>>>> second thread. So in the do_anonymous_page() here, we should use
>>>>>>> update_mmu_tlb() instead of update_mmu_cache() on the second thread.
>>>>>>>
>>>>>>> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
>>>>>>> Reviewed-by: Muchun Song <songmuchun@bytedance.com>
>>>>>>> ---
>>>>>>> v1: https://lore.kernel.org/lkml/20220924053239.91661-1-zhengqi.arch@bytedance.com/
>>>>>>>
>>>>>>> Changelog in v1 -> v2:
>>>>>>>     - change the subject and commit message (David)
>>>>>>>
>>>>>>>     mm/memory.c | 2 +-
>>>>>>>     1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>>>
>>>>>>> diff --git a/mm/memory.c b/mm/memory.c
>>>>>>> index 118e5f023597..9e11c783ba0e 100644
>>>>>>> --- a/mm/memory.c
>>>>>>> +++ b/mm/memory.c
>>>>>>> @@ -4122,7 +4122,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
>>>>>>>         vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address,
>>>>>>>                 &vmf->ptl);
>>>>>>>         if (!pte_none(*vmf->pte)) {
>>>>>>> -        update_mmu_cache(vma, vmf->address, vmf->pte);
>>>>>>> +        update_mmu_tlb(vma, vmf->address, vmf->pte);
>>>>>>>             goto release;
>>>>>>>         }
>>>>>>
>>>>>>
>>>>>> Staring at 7df676974359, it indeed looks like an accidental use [nothing else in that patch uses update_mmu_cache].
>>>>>>
>>>>>> So it looks good to me, but a confirmation from Bibo Mao might be good.
>>>>>
>>>>> Thanks, and Hi Bibo, any comments here? :)
>>>>
>>>> update_mmu_tlb is defined as empty on loongarch, maybe some lines should
>>>> be added in file arch/loongarch/include/asm/pgtable.h like this:
>>>
>>> Seems like a bug? Because there are many other places where
>>> update_mmu_tlb() is called.
>>>
>>>>
>>>> +#define __HAVE_ARCH_UPDATE_MMU_TLB
>>>> +#define update_mmu_tlb  update_mmu_cache
>>>
>>> If so, I can make the above as a separate fix patch.
>> It sounds good to me.
>>
>> Huacai, do you have any comments?
>  From my point of view, LoongArch need a fix for this.

OK, will do it in the next version. Thanks. :)

> 
> Huacai
>>
>> regards
>> bibo, mao
>>>
>>> Thanks,
>>> Qi
>>>
>>>>
>>>> regards
>>>> bibo mao
>>>>>
>>>>>>
>>>>>
>>>>
>>>
> 
> 
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-- 
Thanks,
Qi