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From: Steven Price <steven.price@arm.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: "Mark Rutland" <Mark.Rutland@arm.com>,
	x86@kernel.org, "Arnd Bergmann" <arnd@arndb.de>,
	"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	"Will Deacon" <will.deacon@arm.com>,
	linux-kernel@vger.kernel.org,
	"Russell King" <linux@armlinux.org.uk>,
	linux-mm@kvack.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>,
	linux-arm-kernel@lists.infradead.org, "Liang,
	Kan" <kan.liang@linux.intel.com>
Subject: Re: [PATCH v3 03/34] arm: mm: Add p?d_large() definitions
Date: Mon, 4 Mar 2019 11:56:13 +0000	[thread overview]
Message-ID: <974310a0-0114-9a0c-9041-4e0394c4b9aa@arm.com> (raw)
In-Reply-To: <20190301214715.hyzy5tevvwgki4w5@kshutemo-mobl1>

On 01/03/2019 21:47, Kirill A. Shutemov wrote:
> On Wed, Feb 27, 2019 at 05:05:37PM +0000, Steven Price 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 will be provided by the
>> p?d_large() functions/macros.
>>
>> For arm, we already provide most p?d_large() macros. Add a stub for PUD
>> as we don't have huge pages at that level.
> 
> We do not have PUD for 2- and 3-level paging. Macros from generic header
> should cover it, shouldn't it?
> 

I'm not sure of the reasoning behind this, but levels are folded in a
slightly strange way. arm/include/asm/pgtable.h defines
__ARCH_USE_5LEVEL_HACK which means:

PGD has 2048 (2-level) or 4 (3-level) entries which are always
considered 'present' (pgd_present() returns 1 defined in
asm-generic/pgtables-nop4d-hack.h).

P4D has 1 entry which is always present (see asm-generic/5level-fixup.h)

PUD has 1 entry (see asm-generic/pgtable-nop4d-hack.h). This is always
present for 2-level, and present only if the first level of real page
table is present with a 3-level.

PMD/PTE are as you might expect.

So in terms of tables which are more than one entry you have PGD,
(optionally) PMD, PTE. But the levels which actually read the table
entries are PUD, PMD, PTE.

This means that the corresponding p?d_large() macros are needed for
PUD/PMD as that is where the actual entries are read. The asm-generic
files provide the definitions for PGD/P4D.

Steve

  reply	other threads:[~2019-03-04 11:56 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-27 17:05 [PATCH v3 00/34] Convert x86 & arm64 to use generic page walk Steven Price
2019-02-27 17:05 ` [PATCH v3 01/34] alpha: mm: Add p?d_large() definitions Steven Price
2019-02-27 17:05 ` [PATCH v3 02/34] arc: " Steven Price
2019-02-27 18:18   ` Vineet Gupta
2019-02-27 17:05 ` [PATCH v3 03/34] arm: " Steven Price
2019-03-01 21:47   ` Kirill A. Shutemov
2019-03-04 11:56     ` Steven Price [this message]
2019-03-04 13:10       ` Kirill A. Shutemov
2019-02-27 17:05 ` [PATCH v3 04/34] arm64: " Steven Price
2019-02-27 17:05 ` [PATCH v3 05/34] c6x: " Steven Price
2019-03-01 21:48   ` Kirill A. Shutemov
2019-03-04 12:01     ` Steven Price
2019-03-04 13:11       ` Kirill A. Shutemov
2019-02-27 17:05 ` [PATCH v3 06/34] csky: " Steven Price
2019-03-01 21:51   ` Kirill A. Shutemov
2019-02-27 17:05 ` [PATCH v3 07/34] hexagon: " Steven Price
2019-02-27 17:05 ` [PATCH v3 08/34] ia64: " Steven Price
2019-03-01 21:57   ` Kirill A. Shutemov
2019-03-04 13:16     ` Steven Price
2019-03-04 19:06       ` Luck, Tony
2019-03-06 13:45         ` Steven Price
2019-02-27 17:05 ` [PATCH v3 09/34] m68k: " Steven Price
2019-02-27 19:27   ` Geert Uytterhoeven
2019-02-28 11:36     ` Mike Rapoport
2019-02-28 11:53       ` Geert Uytterhoeven
2019-02-28 12:04         ` Steven Price
2019-03-01 11:45           ` Mike Rapoport
2019-02-27 17:05 ` [PATCH v3 10/34] microblaze: " Steven Price
2019-02-27 17:05 ` [PATCH v3 11/34] mips: " Steven Price
2019-02-28  2:15   ` Paul Burton
2019-02-28 12:11     ` Steven Price
2019-02-28 18:55       ` Paul Burton
2019-03-01 11:02         ` Steven Price
2019-02-27 17:05 ` [PATCH v3 12/34] nds32: " Steven Price
2019-02-27 17:05 ` [PATCH v3 13/34] nios2: " Steven Price
2019-02-27 17:05 ` [PATCH v3 14/34] openrisc: " Steven Price
2019-02-27 17:05 ` [PATCH v3 15/34] parisc: " Steven Price
2019-02-27 18:54   ` Helge Deller
2019-03-01 22:12     ` Kirill A. Shutemov
2019-03-05 21:45       ` Helge Deller
2019-02-27 17:05 ` [PATCH v3 16/34] powerpc: " Steven Price
2019-02-27 17:05 ` [PATCH v3 17/34] riscv: " Steven Price
2019-02-27 17:05 ` [PATCH v3 18/34] s390: " Steven Price
2019-02-27 17:40   ` Martin Schwidefsky
2019-02-28 11:43     ` Steven Price
2019-02-27 17:05 ` [PATCH v3 19/34] sh: " Steven Price
2019-02-27 17:05 ` [PATCH v3 20/34] sparc: " Steven Price
2019-02-27 18:38   ` David Miller
2019-02-28 11:49     ` Steven Price
2019-02-27 17:05 ` [PATCH v3 21/34] um: " Steven Price
2019-02-27 17:05 ` [PATCH v3 22/34] unicore32: " Steven Price
2019-02-27 17:05 ` [PATCH v3 23/34] xtensa: " Steven Price
2019-02-27 17:29   ` Max Filippov
2019-02-27 17:05 ` [PATCH v3 24/34] mm: Add generic p?d_large() macros Steven Price
2019-02-27 17:05 ` [PATCH v3 25/34] mm: pagewalk: Add p4d_entry() and pgd_entry() Steven Price
2019-02-27 17:06 ` [PATCH v3 26/34] mm: pagewalk: Allow walking without vma Steven Price
2019-02-27 17:06 ` [PATCH v3 27/34] mm: pagewalk: Add 'depth' parameter to pte_hole Steven Price
2019-02-27 17:38   ` Dave Hansen
2019-02-28 11:28     ` Steven Price
2019-02-28 19:00       ` Dave Hansen
2019-03-01 11:24         ` Steven Price
2019-02-27 17:06 ` [PATCH v3 28/34] mm: pagewalk: Add test_p?d callbacks Steven Price
2019-02-27 17:06 ` [PATCH v3 29/34] arm64: mm: Convert mm/dump.c to use walk_page_range() Steven Price
2019-02-27 17:06 ` [PATCH v3 30/34] x86/mm: Point to struct seq_file from struct pg_state Steven Price
2019-02-27 17:06 ` [PATCH v3 31/34] x86/mm+efi: Convert ptdump_walk_pgd_level() to take a mm_struct Steven Price
2019-02-27 17:06 ` [PATCH v3 32/34] x86/mm: Convert ptdump_walk_pgd_level_debugfs() to take an mm_struct Steven Price
2019-02-27 17:06 ` [PATCH v3 33/34] x86/mm: Convert ptdump_walk_pgd_level_core() " Steven Price
2019-02-27 17:06 ` [PATCH v3 34/34] x86: mm: Convert dump_pagetables to use walk_page_range Steven Price

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