From: Steven Price <steven.price@arm.com>
To: Mike Rapoport <rppt@linux.ibm.com>
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, 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 v5 10/19] mm: pagewalk: Add p4d_entry() and pgd_entry()
Date: Fri, 22 Mar 2019 10:11:59 +0000 [thread overview]
Message-ID: <03f5ad0f-2450-c53f-b1e6-d2c0f2d4879c@arm.com> (raw)
In-Reply-To: <20190321211510.GA27213@rapoport-lnx>
On 21/03/2019 21:15, Mike Rapoport wrote:
> On Thu, Mar 21, 2019 at 02:19:44PM +0000, Steven Price wrote:
>> pgd_entry() and pud_entry() were removed by commit 0b1fbfe50006c410
>> ("mm/pagewalk: remove pgd_entry() and pud_entry()") because there were
>> no users. We're about to add users so reintroduce them, along with
>> p4d_entry() as we now have 5 levels of tables.
>>
>> Note that commit a00cc7d9dd93d66a ("mm, x86: add support for
>> PUD-sized transparent hugepages") already re-added pud_entry() but with
>> different semantics to the other callbacks. Since there have never
>> been upstream users of this, revert the semantics back to match the
>> other callbacks. This means pud_entry() is called for all entries, not
>> just transparent huge pages.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>> include/linux/mm.h | 9 ++++++---
>> mm/pagewalk.c | 27 ++++++++++++++++-----------
>> 2 files changed, 22 insertions(+), 14 deletions(-)
>>
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index 76769749b5a5..2983f2396a72 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -1367,10 +1367,9 @@ void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
>>
>> /**
>> * mm_walk - callbacks for walk_page_range
>> + * @pgd_entry: if set, called for each non-empty PGD (top-level) entry
>> + * @p4d_entry: if set, called for each non-empty P4D (1st-level) entry
>
> IMHO, p4d implies the 4th level :)
You have a good point there... I was simply working back from the
existing definitions (below) of PTE:4th, PMD:3rd, PUD:2nd. But it's
already somewhat broken by PGD:0th and my cop-out was calling it "top".
> I think it would make more sense to start counting from PTE rather than
> from PGD. Then it would be consistent across architectures with fewer
> levels.
It would also be the opposite way round to architectures such as Arm
which number their levels, for example [1] refers to levels 0-3 (with 3
being PTE in Linux terms).
[1]
https://developer.arm.com/docs/100940/latest/translation-tables-in-armv8-a
Probably the least confusing thing is to drop the level numbers in
brackets since I don't believe they directly match any architecture, and
hopefully any user of the page walking code is already familiar with the
P?D terms used by the kernel.
Steve
>> * @pud_entry: if set, called for each non-empty PUD (2nd-level) entry
>> - * this handler should only handle pud_trans_huge() puds.
>> - * the pmd_entry or pte_entry callbacks will be used for
>> - * regular PUDs.
>> * @pmd_entry: if set, called for each non-empty PMD (3rd-level) entry
>> * this handler is required to be able to handle
>> * pmd_trans_huge() pmds. They may simply choose to
>> @@ -1390,6 +1389,10 @@ void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
>> * (see the comment on walk_page_range() for more details)
>> */
>> struct mm_walk {
>> + int (*pgd_entry)(pgd_t *pgd, unsigned long addr,
>> + unsigned long next, struct mm_walk *walk);
>> + int (*p4d_entry)(p4d_t *p4d, unsigned long addr,
>> + unsigned long next, struct mm_walk *walk);
>> int (*pud_entry)(pud_t *pud, unsigned long addr,
>> unsigned long next, struct mm_walk *walk);
>> int (*pmd_entry)(pmd_t *pmd, unsigned long addr,
>> diff --git a/mm/pagewalk.c b/mm/pagewalk.c
>> index c3084ff2569d..98373a9f88b8 100644
>> --- a/mm/pagewalk.c
>> +++ b/mm/pagewalk.c
>> @@ -90,15 +90,9 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
>> }
>>
>> if (walk->pud_entry) {
>> - spinlock_t *ptl = pud_trans_huge_lock(pud, walk->vma);
>> -
>> - if (ptl) {
>> - err = walk->pud_entry(pud, addr, next, walk);
>> - spin_unlock(ptl);
>> - if (err)
>> - break;
>> - continue;
>> - }
>> + err = walk->pud_entry(pud, addr, next, walk);
>> + if (err)
>> + break;
>> }
>>
>> split_huge_pud(walk->vma, pud, addr);
>> @@ -131,7 +125,12 @@ static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
>> break;
>> continue;
>> }
>> - if (walk->pmd_entry || walk->pte_entry)
>> + if (walk->p4d_entry) {
>> + err = walk->p4d_entry(p4d, addr, next, walk);
>> + if (err)
>> + break;
>> + }
>> + if (walk->pud_entry || walk->pmd_entry || walk->pte_entry)
>> err = walk_pud_range(p4d, addr, next, walk);
>> if (err)
>> break;
>> @@ -157,7 +156,13 @@ static int walk_pgd_range(unsigned long addr, unsigned long end,
>> break;
>> continue;
>> }
>> - if (walk->pmd_entry || walk->pte_entry)
>> + if (walk->pgd_entry) {
>> + err = walk->pgd_entry(pgd, addr, next, walk);
>> + if (err)
>> + break;
>> + }
>> + if (walk->p4d_entry || walk->pud_entry || walk->pmd_entry ||
>> + walk->pte_entry)
>> err = walk_p4d_range(pgd, addr, next, walk);
>> if (err)
>> break;
>> --
>> 2.20.1
>>
>
next prev parent reply other threads:[~2019-03-22 10:12 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-21 14:19 [PATCH v5 00/19] Convert x86 & arm64 to use generic page walk Steven Price
2019-03-21 14:19 ` [PATCH v5 01/19] arc: mm: Add p?d_large() definitions Steven Price
2019-03-21 14:19 ` [PATCH v5 02/19] arm64: " Steven Price
2019-03-21 14:19 ` [PATCH v5 03/19] mips: " Steven Price
2019-03-21 14:19 ` [PATCH v5 04/19] powerpc: " Steven Price
2019-03-21 14:19 ` [PATCH v5 05/19] riscv: " Steven Price
2019-03-21 14:19 ` [PATCH v5 06/19] s390: " Steven Price
2019-03-21 14:19 ` [PATCH v5 07/19] sparc: " Steven Price
2019-03-21 14:19 ` [PATCH v5 08/19] x86: " Steven Price
2019-03-21 14:19 ` [PATCH v5 09/19] mm: Add generic p?d_large() macros Steven Price
2019-03-21 14:19 ` [PATCH v5 10/19] mm: pagewalk: Add p4d_entry() and pgd_entry() Steven Price
2019-03-21 21:15 ` Mike Rapoport
2019-03-22 10:11 ` Steven Price [this message]
2019-03-22 10:29 ` Mike Rapoport
2019-03-22 10:37 ` Steven Price
2019-03-21 14:19 ` [PATCH v5 11/19] mm: pagewalk: Allow walking without vma Steven Price
2019-03-21 14:19 ` [PATCH v5 12/19] mm: pagewalk: Add test_p?d callbacks Steven Price
2019-03-21 14:19 ` [PATCH v5 13/19] arm64: mm: Convert mm/dump.c to use walk_page_range() Steven Price
2019-03-21 14:19 ` [PATCH v5 14/19] x86: mm: Don't display pages which aren't present in debugfs Steven Price
2019-03-21 14:19 ` [PATCH v5 15/19] x86: mm: Point to struct seq_file from struct pg_state Steven Price
2019-03-21 14:19 ` [PATCH v5 16/19] x86: mm+efi: Convert ptdump_walk_pgd_level() to take a mm_struct Steven Price
2019-03-21 14:19 ` [PATCH v5 17/19] x86: mm: Convert ptdump_walk_pgd_level_debugfs() to take an mm_struct Steven Price
2019-03-21 14:19 ` [PATCH v5 18/19] x86: mm: Convert ptdump_walk_pgd_level_core() " Steven Price
2019-03-21 14:19 ` [PATCH v5 19/19] x86: mm: Convert dump_pagetables to use walk_page_range Steven Price
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