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[217.140.101.70]) by mx.google.com with ESMTP id b23si3116379ede.163.2019.03.22.03.12.04 for ; Fri, 22 Mar 2019 03:12:05 -0700 (PDT) Received-SPF: pass (google.com: domain of steven.price@arm.com designates 217.140.101.70 as permitted sender) client-ip=217.140.101.70; Authentication-Results: mx.google.com; spf=pass (google.com: domain of steven.price@arm.com designates 217.140.101.70 as permitted sender) smtp.mailfrom=steven.price@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E6E79374; Fri, 22 Mar 2019 03:12:03 -0700 (PDT) Received: from [10.1.196.69] (e112269-lin.cambridge.arm.com [10.1.196.69]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C869E3F575; Fri, 22 Mar 2019 03:12:00 -0700 (PDT) Subject: Re: [PATCH v5 10/19] mm: pagewalk: Add p4d_entry() and pgd_entry() To: Mike Rapoport Cc: Mark Rutland , x86@kernel.org, Arnd Bergmann , Ard Biesheuvel , Peter Zijlstra , Catalin Marinas , Dave Hansen , Will Deacon , linux-kernel@vger.kernel.org, linux-mm@kvack.org, =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Ingo Molnar , Borislav Petkov , Andy Lutomirski , "H. Peter Anvin" , James Morse , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, "Liang, Kan" References: <20190321141953.31960-1-steven.price@arm.com> <20190321141953.31960-11-steven.price@arm.com> <20190321211510.GA27213@rapoport-lnx> From: Steven Price Message-ID: <03f5ad0f-2450-c53f-b1e6-d2c0f2d4879c@arm.com> Date: Fri, 22 Mar 2019 10:11:59 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <20190321211510.GA27213@rapoport-lnx> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 >> --- >> 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 >> >