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From: Steven Price <steven.price@arm.com>
To: Michael Ellerman <mpe@ellerman.id.au>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org
Cc: "Mark Rutland" <mark.rutland@arm.com>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"Andy Lutomirski" <luto@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"James Morse" <james.morse@arm.com>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Will Deacon" <will@kernel.org>,
	linux-arm-kernel@lists.infradead.org, "Liang,
	Kan" <kan.liang@linux.intel.com>
Subject: Re: [PATCH v17 01/23] mm: Add generic p?d_leaf() macros
Date: Fri, 20 Dec 2019 11:48:32 +0000
Message-ID: <0951d79f-919a-4a9d-00f7-b40be96af118@arm.com> (raw)
In-Reply-To: <878sn8mtgt.fsf@mpe.ellerman.id.au>

On 19/12/2019 11:43, Michael Ellerman wrote:
> Steven Price <steven.price@arm.com> writes:
>> Exposing the pud/pgd levels of the page tables to walk_page_range() means
>> we may come across the exotic large mappings that come with large areas
>> of contiguous memory (such as the kernel's linear map).
>>
>> For architectures that don't provide all p?d_leaf() macros, provide
>> generic do nothing default that are suitable where there cannot be leaf
>> pages at that level. Futher patches will add implementations for
>> individual architectures.
>>
>> The name p?d_leaf() is chosen to minimize the confusion with existing
>> uses of "large" pages and "huge" pages which do not necessary mean that
>> the entry is a leaf (for example it may be a set of contiguous entries
>> that only take 1 TLB slot). For the purpose of walking the page tables
>> we don't need to know how it will be represented in the TLB, but we do
>> need to know for sure if it is a leaf of the tree.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> Acked-by: Mark Rutland <mark.rutland@arm.com>
>> ---
>>  include/asm-generic/pgtable.h | 20 ++++++++++++++++++++
>>  1 file changed, 20 insertions(+)
>>
>> diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
>> index 798ea36a0549..e2e2bef07dd2 100644
>> --- a/include/asm-generic/pgtable.h
>> +++ b/include/asm-generic/pgtable.h
>> @@ -1238,4 +1238,24 @@ static inline bool arch_has_pfn_modify_check(void)
>>  #define mm_pmd_folded(mm)	__is_defined(__PAGETABLE_PMD_FOLDED)
>>  #endif
>>  
>> +/*
>> + * p?d_leaf() - true if this entry is a final mapping to a physical address.
>> + * This differs from p?d_huge() by the fact that they are always available (if
>> + * the architecture supports large pages at the appropriate level) even
>> + * if CONFIG_HUGETLB_PAGE is not defined.
>> + * Only meaningful when called on a valid entry.
>> + */
>> +#ifndef pgd_leaf
>> +#define pgd_leaf(x)	0
>> +#endif
>> +#ifndef p4d_leaf
>> +#define p4d_leaf(x)	0
>> +#endif
>> +#ifndef pud_leaf
>> +#define pud_leaf(x)	0
>> +#endif
>> +#ifndef pmd_leaf
>> +#define pmd_leaf(x)	0
>> +#endif
> 
> Any reason you made these #defines rather than static inlines?

No strong reason - but these have to be #defines in the arch overrides
so the #ifndef works, so I was being consistent here. I guess a static
inline might avoid warnings although I haven't seen any.

Steve

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Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-18 16:23 [PATCH v17 00/23] Generic page walk and ptdump Steven Price
2019-12-18 16:23 ` [PATCH v17 01/23] mm: Add generic p?d_leaf() macros Steven Price
2019-12-19 11:43   ` Michael Ellerman
2019-12-20 11:48     ` Steven Price [this message]
2019-12-21 10:35       ` Michael Ellerman
2019-12-18 16:23 ` [PATCH v17 02/23] arc: mm: Add p?d_leaf() definitions Steven Price
2019-12-18 16:23 ` [PATCH v17 03/23] arm: " Steven Price
2019-12-18 16:23 ` [PATCH v17 04/23] arm64: " Steven Price
2019-12-18 16:23 ` [PATCH v17 05/23] mips: " Steven Price
2019-12-18 16:23 ` [PATCH v17 06/23] powerpc: " Steven Price
2019-12-19 11:49   ` Michael Ellerman
2019-12-20 11:53     ` Steven Price
2019-12-18 16:23 ` [PATCH v17 07/23] riscv: " Steven Price
2019-12-18 16:23 ` [PATCH v17 08/23] s390: " Steven Price
2019-12-18 16:23 ` [PATCH v17 09/23] sparc: " Steven Price
2019-12-18 16:23 ` [PATCH v17 10/23] x86: " Steven Price
2019-12-18 16:23 ` [PATCH v17 11/23] mm: pagewalk: Add p4d_entry() and pgd_entry() Steven Price
2019-12-19 14:25   ` Thomas Hellström (VMware)
2019-12-20 15:35     ` Steven Price
2019-12-18 16:23 ` [PATCH v17 12/23] mm: pagewalk: Allow walking without vma Steven Price
2019-12-18 16:23 ` [PATCH v17 13/23] mm: pagewalk: Don't lock PTEs for walk_page_range_novma() Steven Price
2019-12-18 16:23 ` [PATCH v17 14/23] mm: pagewalk: fix termination condition in walk_pte_range() Steven Price
2019-12-18 16:23 ` [PATCH v17 15/23] mm: pagewalk: Add 'depth' parameter to pte_hole Steven Price
2019-12-18 16:23 ` [PATCH v17 16/23] x86: mm: Point to struct seq_file from struct pg_state Steven Price
2019-12-18 16:23 ` [PATCH v17 17/23] x86: mm+efi: Convert ptdump_walk_pgd_level() to take a mm_struct Steven Price
2019-12-18 16:23 ` [PATCH v17 18/23] x86: mm: Convert ptdump_walk_pgd_level_debugfs() to take an mm_struct Steven Price
2019-12-18 16:23 ` [PATCH v17 19/23] mm: Add generic ptdump Steven Price
2019-12-18 16:23 ` [PATCH v17 20/23] x86: mm: Convert dump_pagetables to use walk_page_range Steven Price
2019-12-18 16:24 ` [PATCH v17 21/23] arm64: mm: Convert mm/dump.c to use walk_page_range() Steven Price
2020-02-16 16:25   ` Ard Biesheuvel
2020-02-17 10:01     ` Steven Price
2020-02-17 10:16       ` Ard Biesheuvel
2019-12-18 16:24 ` [PATCH v17 22/23] arm64: mm: Display non-present entries in ptdump Steven Price
2019-12-18 16:24 ` [PATCH v17 23/23] mm: ptdump: Reduce level numbers by 1 in note_page() Steven Price

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