linux-kernel - Re: [PATCH v17 06/23] powerpc: mm: Add p?d_leaf() definitions

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Message-ID: <e99a9857-e9f4-588a-ad12-4d5f3a9de739@arm.com>
Date:   Fri, 20 Dec 2019 11:53:44 +0000
From:   Steven Price <steven.price@....com>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org
Cc:     Mark Rutland <Mark.Rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Paul Mackerras <paulus@...ba.org>,
        "H. Peter Anvin" <hpa@...or.com>, Will Deacon <will@...nel.org>,
        "Liang, Kan" <kan.liang@...ux.intel.com>, x86@...nel.org,
        Ingo Molnar <mingo@...hat.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Arnd Bergmann <arnd@...db.de>, kvm-ppc@...r.kernel.org,
        Jérôme Glisse <jglisse@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-arm-kernel@...ts.infradead.org,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        linux-kernel@...r.kernel.org, James Morse <james.morse@....com>,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v17 06/23] powerpc: mm: Add p?d_leaf() definitions

On 19/12/2019 11:49, Michael Ellerman wrote:
> Steven Price <steven.price@....com> writes:
>> 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_leaf() functions/macros.
>>
>> For powerpc p?d_is_leaf() functions already exist. Export them using the
>> new p?d_leaf() name.
>>
>> CC: Benjamin Herrenschmidt <benh@...nel.crashing.org>
>> CC: Paul Mackerras <paulus@...ba.org>
>> CC: Michael Ellerman <mpe@...erman.id.au>
>> CC: linuxppc-dev@...ts.ozlabs.org
>> CC: kvm-ppc@...r.kernel.org
>> Signed-off-by: Steven Price <steven.price@....com>
>> ---
>>  arch/powerpc/include/asm/book3s/64/pgtable.h | 3 +++
>>  1 file changed, 3 insertions(+)
> 
> We have fallback versions of our pmd_is_leaf() etc. in
> arch/powerpc/include/asm/pgtable.h, eg:
> 
> #ifndef pmd_is_leaf
> #define pmd_is_leaf pmd_is_leaf
> static inline bool pmd_is_leaf(pmd_t pmd)
> {
> 	return false;
> }
> #endif
> 
> Because we support several different MMUs and most of them don't need to
> do anything.
> 
> So we could put the compatibility #defines to your names along with the
> fallback versions in asm/pgtable.h, rather than in
> asm/book3s/64/pgtable.h
> 
> But I see you also have fallbacks for your versions, so it probably
> doesn't matter either way.
> 
> So I'm OK with this version, unless you think there's a compelling
> reason to do the compatibility #defines in our asm/pgtable.h

I was thinking that (assuming this series actually gets merged this
time), the p?d_is_leaf() versions could be removed and replaced by
p?d_leaf() in the future. Since the fallbacks are in the asm-generic
code it makes sense for the pmd_leaf() definitions to be next to the
non-fallback versions.

> Acked-by: Michael Ellerman <mpe@...erman.id.au>

Thanks!

Steve

> cheers
> 
> 
>> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
>> index b01624e5c467..201a69e6a355 100644
>> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
>> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
>> @@ -1355,18 +1355,21 @@ static inline bool is_pte_rw_upgrade(unsigned long old_val, unsigned long new_va
>>   * Like pmd_huge() and pmd_large(), but works regardless of config options
>>   */
>>  #define pmd_is_leaf pmd_is_leaf
>> +#define pmd_leaf pmd_is_leaf
>>  static inline bool pmd_is_leaf(pmd_t pmd)
>>  {
>>  	return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_PTE));
>>  }
>>  
>>  #define pud_is_leaf pud_is_leaf
>> +#define pud_leaf pud_is_leaf
>>  static inline bool pud_is_leaf(pud_t pud)
>>  {
>>  	return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PTE));
>>  }
>>  
>>  #define pgd_is_leaf pgd_is_leaf
>> +#define pgd_leaf pgd_is_leaf
>>  static inline bool pgd_is_leaf(pgd_t pgd)
>>  {
>>  	return !!(pgd_raw(pgd) & cpu_to_be64(_PAGE_PTE));
>> -- 
>> 2.20.1
> 
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