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Tue, 8 Sep 2020 14:15:58 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1FB7CA4069; Tue, 8 Sep 2020 14:15:58 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7DB9EA406D; Tue, 8 Sep 2020 14:15:56 +0000 (GMT) Received: from oc3871087118.ibm.com (unknown [9.145.58.21]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Tue, 8 Sep 2020 14:15:56 +0000 (GMT) Date: Tue, 8 Sep 2020 16:15:55 +0200 From: Alexander Gordeev To: Christophe Leroy Cc: Michael Ellerman , Gerald Schaefer , Jason Gunthorpe , John Hubbard , Peter Zijlstra , Dave Hansen , linux-mm , Paul Mackerras , linux-sparc , Claudio Imbrenda , Will Deacon , linux-arch , linux-s390 , Vasily Gorbik , Richard Weinberger , linux-x86 , Russell King , Christian Borntraeger , Ingo Molnar , Catalin Marinas , Andrey Ryabinin , Heiko Carstens , Arnd Bergmann , Jeff Dike , linux-um , Borislav Petkov , Andy Lutomirski , Thomas Gleixner , linux-arm , linux-power , LKML , Andrew Morton , Linus Torvalds , Mike Rapoport Subject: Re: [RFC PATCH v2 2/3] mm: make pXd_addr_end() functions page-table entry aware Message-ID: <20200908141554.GA20558@oc3871087118.ibm.com> References: <20200907180058.64880-1-gerald.schaefer@linux.ibm.com> <20200907180058.64880-3-gerald.schaefer@linux.ibm.com> <31dfb3ed-a0cc-3024-d389-ab9bd19e881f@csgroup.eu> <20200908074638.GA19099@oc3871087118.ibm.com> <5d4f5546-afd0-0b8f-664d-700ae346b9ec@csgroup.eu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5d4f5546-afd0-0b8f-664d-700ae346b9ec@csgroup.eu> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-09-08_07:2020-09-08,2020-09-08 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 mlxscore=0 suspectscore=0 bulkscore=0 phishscore=0 mlxlogscore=999 clxscore=1015 priorityscore=1501 impostorscore=0 lowpriorityscore=0 malwarescore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009080133 X-Rspamd-Queue-Id: 5CB661819E772 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam01 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 Tue, Sep 08, 2020 at 10:16:49AM +0200, Christophe Leroy wrote: > >Yes, and also two more sources :/ > > arch/powerpc/mm/kasan/8xx.c > > arch/powerpc/mm/kasan/kasan_init_32.c > > > >But these two are not quite obvious wrt pgd_addr_end() used > >while traversing pmds. Could you please clarify a bit? > > > > > >diff --git a/arch/powerpc/mm/kasan/8xx.c b/arch/powerpc/mm/kasan/8xx.c > >index 2784224..89c5053 100644 > >--- a/arch/powerpc/mm/kasan/8xx.c > >+++ b/arch/powerpc/mm/kasan/8xx.c > >@@ -15,8 +15,8 @@ > > for (k_cur = k_start; k_cur != k_end; k_cur = k_next, pmd += 2, block += SZ_8M) { > > pte_basic_t *new; > >- k_next = pgd_addr_end(k_cur, k_end); > >- k_next = pgd_addr_end(k_next, k_end); > >+ k_next = pmd_addr_end(k_cur, k_end); > >+ k_next = pmd_addr_end(k_next, k_end); > > No, I don't think so. > On powerpc32 we have only two levels, so pgd and pmd are more or > less the same. > But pmd_addr_end() as defined in include/asm-generic/pgtable-nopmd.h > is a no-op, so I don't think it will work. > > It is likely that this function should iterate on pgd, then you get > pmd = pmd_offset(pud_offset(p4d_offset(pgd))); It looks like the code iterates over single pmd table while using pgd_addr_end() only to skip all the middle levels and bail out from the loop. I would be wary for switching from pmds to pgds, since we are trying to minimize impact (especially functional) and the rework does not seem that obvious. Assuming pmd and pgd are the same would actually such approach work for now? diff --git a/arch/powerpc/mm/kasan/8xx.c b/arch/powerpc/mm/kasan/8xx.c index 2784224..94466cc 100644 --- a/arch/powerpc/mm/kasan/8xx.c +++ b/arch/powerpc/mm/kasan/8xx.c @@ -15,8 +15,8 @@ for (k_cur = k_start; k_cur != k_end; k_cur = k_next, pmd += 2, block += SZ_8M) { pte_basic_t *new; - k_next = pgd_addr_end(k_cur, k_end); - k_next = pgd_addr_end(k_next, k_end); + k_next = pgd_addr_end(__pgd(pmd_val(*pmd)), k_cur, k_end); + k_next = pgd_addr_end(__pgd(pmd_val(*(pmd + 1))), k_next, k_end); if ((void *)pmd_page_vaddr(*pmd) != kasan_early_shadow_pte) continue; diff --git a/arch/powerpc/mm/kasan/kasan_init_32.c b/arch/powerpc/mm/kasan/kasan_init_32.c index fb29404..c0bcd64 100644 --- a/arch/powerpc/mm/kasan/kasan_init_32.c +++ b/arch/powerpc/mm/kasan/kasan_init_32.c @@ -38,7 +38,7 @@ int __init kasan_init_shadow_page_tables(unsigned long k_start, unsigned long k_ for (k_cur = k_start; k_cur != k_end; k_cur = k_next, pmd++) { pte_t *new; - k_next = pgd_addr_end(k_cur, k_end); + k_next = pgd_addr_end(__pgd(pmd_val(*pmd)), k_cur, k_end); if ((void *)pmd_page_vaddr(*pmd) != kasan_early_shadow_pte) continue; @@ -196,7 +196,7 @@ void __init kasan_early_init(void) kasan_populate_pte(kasan_early_shadow_pte, PAGE_KERNEL); do { - next = pgd_addr_end(addr, end); + next = pgd_addr_end(__pgd(pmd_val(*pmd)), addr, end); pmd_populate_kernel(&init_mm, pmd, kasan_early_shadow_pte); } while (pmd++, addr = next, addr != end); Alternatively we could pass invalid pgd to keep the code structure intact, but that of course is less nice. Thanks! > Christophe