linux-kernel - Re: [PATCH v2 2/3] powerpc: get hugetlbpage handling more generic

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Message-ID: <0f2ea710-1e14-8b80-7480-cea9ffbe9dfa@c-s.fr>
Date:   Tue, 20 Sep 2016 07:22:17 +0200
From:   Christophe Leroy <christophe.leroy@....fr>
To:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Scott Wood <oss@...error.net>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v2 2/3] powerpc: get hugetlbpage handling more generic



Le 20/09/2016 à 04:28, Aneesh Kumar K.V a écrit :
> christophe leroy <christophe.leroy@....fr> writes:
>
>> Le 19/09/2016 à 07:50, Aneesh Kumar K.V a écrit :
>>>
>>> Christophe Leroy <christophe.leroy@....fr> writes:
>>>> +#else
>>>> +static void hugepd_free(struct mmu_gather *tlb, void *hugepte)
>>>> +{
>>>> +	BUG();
>>>> +}
>>>> +
>>>>  #endif
>>>
>>>
>>> I was expecting that BUG will get removed in the next patch. But I don't
>>> see it in the next patch. Considering
>>>
>>> @@ -475,11 +453,10 @@ static void free_hugepd_range(struct mmu_gather *tlb, hugepd_t *hpdp, int pdshif
>>>         for (i = 0; i < num_hugepd; i++, hpdp++)
>>>                 hpdp->pd = 0;
>>>
>>> -#ifdef CONFIG_PPC_FSL_BOOK3E
>>> -	hugepd_free(tlb, hugepte);
>>> -#else
>>> -	pgtable_free_tlb(tlb, hugepte, pdshift - shift);
>>> -#endif
>>> +	if (shift >= pdshift)
>>> +		hugepd_free(tlb, hugepte);
>>> +	else
>>> +		pgtable_free_tlb(tlb, hugepte, pdshift - shift);
>>>  }
>>>
>>> What is that I am missing ?
>>>
>>
>> Previously, call to hugepd_free() was compiled only when #ifdef
>> CONFIG_PPC_FSL_BOOK3E
>> Now, it is compiled at all time, but it should never be called if not
>> CONFIG_PPC_FSL_BOOK3E because we always have shift < pdshift in that case.
>> Then the function needs to be defined anyway but should never be called.
>> Should I just define it static inline {} ?
>>
>
> For 8M with 4K mode, we have shift >= pdshift right ?
>

Yes, thats the reason why in the following patch we get. That way we get 
a real hugepd_free() also for the 8xx.

@@ -366,7 +373,7 @@ int alloc_bootmem_huge_page(struct hstate *hstate)
  }
  #endif

-#ifdef CONFIG_PPC_FSL_BOOK3E
+#if defined(CONFIG_PPC_FSL_BOOK3E) || defined(CONFIG_PPC_8xx)
  #define HUGEPD_FREELIST_SIZE \
  	((PAGE_SIZE - sizeof(struct hugepd_freelist)) / sizeof(pte_t))



Christophe