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From: Steven Price <steven.price@arm.com>
To: Paul Burton <paul.burton@mips.com>
Cc: "Mark Rutland" <Mark.Rutland@arm.com>,
	"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-mips@vger.kernel.org" <linux-mips@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"Liang, Kan" <kan.liang@linux.intel.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"Ingo Molnar" <mingo@redhat.com>,
	"James Hogan" <jhogan@kernel.org>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"Andy Lutomirski" <luto@kernel.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"Ralf Baechle" <ralf@linux-mips.org>,
	"James Morse" <james.morse@arm.com>
Subject: Re: [PATCH v3 11/34] mips: mm: Add p?d_large() definitions
Date: Thu, 28 Feb 2019 12:11:24 +0000	[thread overview]
Message-ID: <74944d83-f3c0-ff02-590e-b7e5abcea485@arm.com> (raw)
In-Reply-To: <20190228021526.bb6m3my46ohb4o6h@pburton-laptop>

On 28/02/2019 02:15, Paul Burton wrote:
> Hi Steven,
> 
> On Wed, Feb 27, 2019 at 05:05:45PM +0000, Steven Price wrote:
>> For mips, we don't support large pages on 32 bit so add stubs returning 0.
> 
> So far so good :)
> 
>> For 64 bit look for _PAGE_HUGE flag being set. This means exposing the
>> flag when !CONFIG_MIPS_HUGE_TLB_SUPPORT.
> 
> Here I have to ask why? We could just return 0 like the mips32 case when
> CONFIG_MIPS_HUGE_TLB_SUPPORT=n, let the compiler optimize the whole
> thing out and avoid redundant work at runtime.
> 
> This could be unified too in asm/pgtable.h - checking for
> CONFIG_MIPS_HUGE_TLB_SUPPORT should be sufficient to cover the mips32
> case along with the subset of mips64 configurations without huge pages.

The intention here is to define a new set of macros/functions which will
always tell us whether we're at the leaf of a page table walk, whether
or not huge pages are compiled into the kernel. Basically this allows
the page walking code to be used on page tables other than user space,
for instance the kernel page tables (which e.g. might use a large
mapping for linear memory even if huge pages are not compiled in) or
page tables from firmware (e.g. EFI on arm64).

I'm not familiar enough with mips to know how it handles things like the
linear map so I don't know how relevant that is, but I'm trying to
introduce a new set of functions which differ from the existing
p?d_huge() macros by not depending on whether these mappings could exist
for a user space VMA (i.e. not depending on HUGETLB support and existing
for all levels that architecturally they can occur at).

Steve

  reply	other threads:[~2019-02-28 12:11 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
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 [this message]
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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