From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id D10601A09F5 for ; Tue, 2 Dec 2014 09:39:03 +1100 (AEDT) Message-ID: <1417473519.7182.6.camel@kernel.crashing.org> Subject: Re: [PATCH 02/10] mm: Add p[te|md] protnone helpers for use by NUMA balancing From: Benjamin Herrenschmidt To: Mel Gorman Date: Tue, 02 Dec 2014 09:38:39 +1100 In-Reply-To: <1416578268-19597-3-git-send-email-mgorman@suse.de> References: <1416578268-19597-1-git-send-email-mgorman@suse.de> <1416578268-19597-3-git-send-email-mgorman@suse.de> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Cc: Rik van Riel , Linus Torvalds , Hugh Dickins , Linux Kernel , Linux-MM , Ingo Molnar , Paul Mackerras , Aneesh Kumar , Sasha Levin , Dave Jones , LinuxPPC-dev , Kirill Shutemov List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, 2014-11-21 at 13:57 +0000, Mel Gorman wrote: > #ifdef CONFIG_NUMA_BALANCING > +/* > + * These work without NUMA balancing but the kernel does not care. See the > + * comment in include/asm-generic/pgtable.h > + */ > +static inline int pte_protnone(pte_t pte) > +{ > + return (pte_val(pte) & > + (_PAGE_PRESENT | _PAGE_USER)) == _PAGE_PRESENT; > +} I would add a comment clarifying that this only works for user pages, ie, this accessor will always return "true" for a kernel page on ppc. > +static inline int pmd_protnone(pmd_t pmd) > +{ > + return pte_protnone(pmd_pte(pmd)); > +} > + > static inline int pte_present(pte_t pte) > { > return pte_val(pte) & _PAGE_NUMA_MASK; > diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h > index 081d6f4..2e25780 100644 > --- a/arch/x86/include/asm/pgtable.h > +++ b/arch/x86/include/asm/pgtable.h > @@ -502,6 +502,22 @@ static inline int pmd_present(pmd_t pmd) > _PAGE_NUMA); > } > > +#ifdef CONFIG_NUMA_BALANCING > +/* > + * These work without NUMA balancing but the kernel does not care. See the > + * comment in include/asm-generic/pgtable.h > + */ > +static inline int pte_protnone(pte_t pte) > +{ > + return pte_flags(pte) & _PAGE_PROTNONE; > +} > + > +static inline int pmd_protnone(pmd_t pmd) > +{ > + return pmd_flags(pmd) & _PAGE_PROTNONE; > +} > +#endif /* CONFIG_NUMA_BALANCING */ > + > static inline int pmd_none(pmd_t pmd) > { > /* Only check low word on 32-bit platforms, since it might be > diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h > index 177d597..d497d08 100644 > --- a/include/asm-generic/pgtable.h > +++ b/include/asm-generic/pgtable.h > @@ -688,6 +688,26 @@ static inline int pmd_trans_unstable(pmd_t *pmd) > #endif > } > > +#ifndef CONFIG_NUMA_BALANCING > +/* > + * Technically a PTE can be PROTNONE even when not doing NUMA balancing but > + * the only case the kernel cares is for NUMA balancing and is only ever set > + * when the VMA is accessible. For PROT_NONE VMAs, the PTEs are not marked > + * _PAGE_PROTNONE so by by default, implement the helper as "always no". It > + * is the responsibility of the caller to distinguish between PROT_NONE > + * protections and NUMA hinting fault protections. > + */ > +static inline int pte_protnone(pte_t pte) > +{ > + return 0; > +} > + > +static inline int pmd_protnone(pmd_t pmd) > +{ > + return 0; > +} > +#endif /* CONFIG_NUMA_BALANCING */ > + > #ifdef CONFIG_NUMA_BALANCING > /* > * _PAGE_NUMA distinguishes between an unmapped page table entry, an entry that