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Tue, 8 Sep 2020 10:17:20 +0200 (CEST) Subject: Re: [RFC PATCH v2 2/3] mm: make pXd_addr_end() functions page-table entry aware To: Alexander Gordeev , Michael Ellerman Cc: 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 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> From: Christophe Leroy Message-ID: <5d4f5546-afd0-0b8f-664d-700ae346b9ec@csgroup.eu> Date: Tue, 8 Sep 2020 10:16:49 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20200908074638.GA19099@oc3871087118.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr X-Rspamd-Queue-Id: E4B431814B0C1 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 Content-Transfer-Encoding: quoted-printable 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: Le 08/09/2020 =C3=A0 09:46, Alexander Gordeev a =C3=A9crit=C2=A0: > On Tue, Sep 08, 2020 at 07:14:38AM +0200, Christophe Leroy wrote: >> You forgot arch/powerpc/mm/book3s64/subpage_prot.c it seems. >=20 > Yes, and also two more sources :/ > arch/powerpc/mm/kasan/8xx.c > arch/powerpc/mm/kasan/kasan_init_32.c >=20 > But these two are not quite obvious wrt pgd_addr_end() used > while traversing pmds. Could you please clarify a bit? >=20 >=20 > 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 =3D k_start; k_cur !=3D k_end; k_cur =3D k_next, pmd +=3D= 2, block +=3D SZ_8M) { > pte_basic_t *new; > =20 > - k_next =3D pgd_addr_end(k_cur, k_end); > - k_next =3D pgd_addr_end(k_next, k_end); > + k_next =3D pmd_addr_end(k_cur, k_end); > + k_next =3D 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=20 the same. But pmd_addr_end() as defined in include/asm-generic/pgtable-nopmd.h is=20 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=20 =3D pmd_offset(pud_offset(p4d_offset(pgd))); > if ((void *)pmd_page_vaddr(*pmd) !=3D kasan_early_shadow_pte) > continue; > =20 > diff --git a/arch/powerpc/mm/kasan/kasan_init_32.c b/arch/powerpc/mm/ka= san/kasan_init_32.c > index fb29404..3f7d6dc6 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 lon= g k_start, unsigned long k_ > for (k_cur =3D k_start; k_cur !=3D k_end; k_cur =3D k_next, pmd++) { > pte_t *new; > =20 > - k_next =3D pgd_addr_end(k_cur, k_end); > + k_next =3D pmd_addr_end(k_cur, k_end); Same here I get, iterate on pgd then get pmd =3D=20 pmd_offset(pud_offset(p4d_offset(pgd))); > if ((void *)pmd_page_vaddr(*pmd) !=3D kasan_early_shadow_pte) > continue; > =20 > @@ -196,7 +196,7 @@ void __init kasan_early_init(void) > kasan_populate_pte(kasan_early_shadow_pte, PAGE_KERNEL); > =20 > do { > - next =3D pgd_addr_end(addr, end); > + next =3D pmd_addr_end(addr, end); > pmd_populate_kernel(&init_mm, pmd, kasan_early_shadow_pte); > } while (pmd++, addr =3D next, addr !=3D end); > =20 >=20 Christophe