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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Fri, 22 Mar 2019 10:29:31 -0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x2MATZDp36044886 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 22 Mar 2019 10:29:35 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 47A9E4C059; Fri, 22 Mar 2019 10:29:35 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 821B54C052; Fri, 22 Mar 2019 10:29:33 +0000 (GMT) Received: from rapoport-lnx (unknown [9.148.206.199]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Fri, 22 Mar 2019 10:29:33 +0000 (GMT) Date: Fri, 22 Mar 2019 12:29:31 +0200 From: Mike Rapoport To: Steven Price 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, =?iso-8859-1?B?Suly9G1l?= Glisse , Ingo Molnar , Borislav Petkov , Andy Lutomirski , "H. Peter Anvin" , James Morse , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, "Liang, Kan" Subject: Re: [PATCH v5 10/19] mm: pagewalk: Add p4d_entry() and pgd_entry() References: <20190321141953.31960-1-steven.price@arm.com> <20190321141953.31960-11-steven.price@arm.com> <20190321211510.GA27213@rapoport-lnx> <03f5ad0f-2450-c53f-b1e6-d2c0f2d4879c@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <03f5ad0f-2450-c53f-b1e6-d2c0f2d4879c@arm.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-TM-AS-GCONF: 00 x-cbid: 19032210-0012-0000-0000-00000305DFC0 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19032210-0013-0000-0000-0000213CFB32 Message-Id: <20190322102930.GA24367@rapoport-lnx> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-03-22_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1903220078 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 22, 2019 at 10:11:59AM +0000, Steven Price wrote: > 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). By consistent I meant that for architectures with fewer levels we won't be describing PTE as level 4 when the architecture only has 2 levels. > [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. That's a fair assumption :) Still, maybe we keep your (top-level) for PGD and use (lowest level) for PTE and drop those in the middle? > 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 > >> > > > -- Sincerely yours, Mike.