linux-kernel - Re: [PATCH v3 18/34] s390: mm: Add p?d

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Message-ID: <0ad6ff76-bbe8-122c-f0e1-54f567dc9753@arm.com>
Date:   Thu, 28 Feb 2019 11:43:29 +0000
From:   Steven Price <steven.price@....com>
To:     Martin Schwidefsky <schwidefsky@...ibm.com>
Cc:     Mark Rutland <Mark.Rutland@....com>, linux-s390@...r.kernel.org,
        x86@...nel.org, Arnd Bergmann <arnd@...db.de>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Will Deacon <will.deacon@....com>,
        linux-kernel@...r.kernel.org,
        Heiko Carstens <heiko.carstens@...ibm.com>, linux-mm@...ck.org,
        Jérôme Glisse <jglisse@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        James Morse <james.morse@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-arm-kernel@...ts.infradead.org,
        "Liang, Kan" <kan.liang@...ux.intel.com>
Subject: Re: [PATCH v3 18/34] s390: mm: Add p?d_large() definitions

On 27/02/2019 17:40, Martin Schwidefsky wrote:
> On Wed, 27 Feb 2019 17:05:52 +0000
> Steven Price <steven.price@....com> wrote:
> 
>> walk_page_range() is going to be allowed to walk page tables other than
>> those of user space. For this it needs to know when it has reached a
>> 'leaf' entry in the page tables. This information is provided by the
>> p?d_large() functions/macros.
>>
>> For s390, we don't support large pages, so add a stub returning 0.
> 
> Well s390 does support 1MB and 2GB large pages, pmd_large() and pud_large()
> are non-empty. We do not support 4TB or 8PB large pages though, which
> makes the patch itself correct. Just the wording is slightly off.

Sorry, you're absolutely right - I'll update the commit message for the
next posting.

Thanks,

Steve

>> CC: Martin Schwidefsky <schwidefsky@...ibm.com>
>> CC: Heiko Carstens <heiko.carstens@...ibm.com>
>> CC: linux-s390@...r.kernel.org
>> Signed-off-by: Steven Price <steven.price@....com>
>> ---
>>  arch/s390/include/asm/pgtable.h | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>> diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
>> index 063732414dfb..9617f1fb69b4 100644
>> --- a/arch/s390/include/asm/pgtable.h
>> +++ b/arch/s390/include/asm/pgtable.h
>> @@ -605,6 +605,11 @@ static inline int pgd_present(pgd_t pgd)
>>  	return (pgd_val(pgd) & _REGION_ENTRY_ORIGIN) != 0UL;
>>  }
>>
>> +static inline int pgd_large(pgd_t pgd)
>> +{
>> +	return 0;
>> +}
>> +
>>  static inline int pgd_none(pgd_t pgd)
>>  {
>>  	if (pgd_folded(pgd))
>> @@ -645,6 +650,11 @@ static inline int p4d_present(p4d_t p4d)
>>  	return (p4d_val(p4d) & _REGION_ENTRY_ORIGIN) != 0UL;
>>  }
>>
>> +static inline int p4d_large(p4d_t p4d)
>> +{
>> +	return 0;
>> +}
>> +
>>  static inline int p4d_none(p4d_t p4d)
>>  {
>>  	if (p4d_folded(p4d))
> 
>