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[217.140.110.172]) by mx.google.com with ESMTP id y54si6381574edb.416.2019.07.23.02.41.21 for ; Tue, 23 Jul 2019 02:41:22 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of mark.rutland@arm.com designates 217.140.110.172 as permitted sender) client-ip=217.140.110.172; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of mark.rutland@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=mark.rutland@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 2D794337; Tue, 23 Jul 2019 02:41:21 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B37613F71A; Tue, 23 Jul 2019 02:41:18 -0700 (PDT) Date: Tue, 23 Jul 2019 10:41:14 +0100 From: Mark Rutland To: Steven Price Cc: linux-mm@kvack.org, Andy Lutomirski , Ard Biesheuvel , Arnd Bergmann , Borislav Petkov , Catalin Marinas , Dave Hansen , Ingo Molnar , James Morse , =?utf-8?B?SsOpcsO0bWU=?= Glisse , Peter Zijlstra , Thomas Gleixner , Will Deacon , x86@kernel.org, "H. Peter Anvin" , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, "Liang, Kan" , Andrew Morton Subject: Re: [PATCH v9 10/21] mm: Add generic p?d_leaf() macros Message-ID: <20190723094113.GA8085@lakrids.cambridge.arm.com> References: <20190722154210.42799-1-steven.price@arm.com> <20190722154210.42799-11-steven.price@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190722154210.42799-11-steven.price@arm.com> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) 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 Mon, Jul 22, 2019 at 04:41:59PM +0100, Steven Price wrote: > Exposing the pud/pgd levels of the page tables to walk_page_range() means > we may come across the exotic large mappings that come with large areas > of contiguous memory (such as the kernel's linear map). > > For architectures that don't provide all p?d_leaf() macros, provide > generic do nothing default that are suitable where there cannot be leaf > pages that that level. > > Signed-off-by: Steven Price Not a big deal, but it would probably make sense for this to be patch 1 in the series, given it defines the semantic of p?d_leaf(), and they're not used until we provide all the architectural implemetnations anyway. It might also be worth pointing out the reasons for this naming, e.g. p?d_large() aren't currently generic, and this name minimizes potential confusion between p?d_{large,huge}(). > --- > include/asm-generic/pgtable.h | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h > index 75d9d68a6de7..46275896ca66 100644 > --- a/include/asm-generic/pgtable.h > +++ b/include/asm-generic/pgtable.h > @@ -1188,4 +1188,23 @@ static inline bool arch_has_pfn_modify_check(void) > #define mm_pmd_folded(mm) __is_defined(__PAGETABLE_PMD_FOLDED) > #endif > > +/* > + * p?d_leaf() - true if this entry is a final mapping to a physical address. > + * This differs from p?d_huge() by the fact that they are always available (if > + * the architecture supports large pages at the appropriate level) even > + * if CONFIG_HUGETLB_PAGE is not defined. > + */ I assume it's only safe to call these on valid entries? I think it would be worth calling that out explicitly. Otherwise, this looks sound to me: Acked-by: Mark Rutland Thanks, Mark. > +#ifndef pgd_leaf > +#define pgd_leaf(x) 0 > +#endif > +#ifndef p4d_leaf > +#define p4d_leaf(x) 0 > +#endif > +#ifndef pud_leaf > +#define pud_leaf(x) 0 > +#endif > +#ifndef pmd_leaf > +#define pmd_leaf(x) 0 > +#endif > + > #endif /* _ASM_GENERIC_PGTABLE_H */ > -- > 2.20.1 >