Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751306AbdGMJtJ (ORCPT ); Thu, 13 Jul 2017 05:49:09 -0400 Received: from mail-qt0-f195.google.com ([209.85.216.195]:32979 "EHLO mail-qt0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750949AbdGMJtH (ORCPT ); Thu, 13 Jul 2017 05:49:07 -0400 MIME-Version: 1.0 In-Reply-To: <20170713075502.GG5525@ram.oc3035372033.ibm.com> References: <1499289735-14220-1-git-send-email-linuxram@us.ibm.com> <1499289735-14220-16-git-send-email-linuxram@us.ibm.com> <20170712152601.3b2f52ed@firefly.ozlabs.ibm.com> <20170713075502.GG5525@ram.oc3035372033.ibm.com> From: Balbir Singh Date: Thu, 13 Jul 2017 19:49:05 +1000 Message-ID: Subject: Re: [RFC v5 15/38] powerpc: helper function to read,write AMR,IAMR,UAMOR registers To: Ram Pai Cc: "open list:LINUX FOR POWERPC (32-BIT AND 64-BIT)" , "linux-kernel@vger.kernel.org" , linux-arch , linux-mm , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , "open list:DOCUMENTATION" , linux-kselftest@vger.kernel.org, Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Anshuman Khandual , Aneesh Kumar KV , Dave Hansen , "Haren Myneni/Beaverton/IBM" , Arnd Bergmann , "akpm@linux-foundation.org" , Jonathan Corbet , Ingo Molnar Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2508 Lines: 74 On Thu, Jul 13, 2017 at 5:55 PM, Ram Pai wrote: > On Wed, Jul 12, 2017 at 03:26:01PM +1000, Balbir Singh wrote: >> On Wed, 5 Jul 2017 14:21:52 -0700 >> Ram Pai wrote: >> >> > Implements helper functions to read and write the key related >> > registers; AMR, IAMR, UAMOR. >> > >> > AMR register tracks the read,write permission of a key >> > IAMR register tracks the execute permission of a key >> > UAMOR register enables and disables a key >> > >> > Signed-off-by: Ram Pai >> > --- >> > arch/powerpc/include/asm/book3s/64/pgtable.h | 60 ++++++++++++++++++++++++++ >> > 1 files changed, 60 insertions(+), 0 deletions(-) >> > >> > diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h >> > index 85bc987..435d6a7 100644 >> > --- a/arch/powerpc/include/asm/book3s/64/pgtable.h >> > +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h >> > @@ -428,6 +428,66 @@ static inline void huge_ptep_set_wrprotect(struct mm_struct *mm, >> > pte_update(mm, addr, ptep, 0, _PAGE_PRIVILEGED, 1); >> > } >> > >> > +#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS >> > + >> > +#include >> > +static inline u64 read_amr(void) >> > +{ >> > + return mfspr(SPRN_AMR); >> > +} >> > +static inline void write_amr(u64 value) >> > +{ >> > + mtspr(SPRN_AMR, value); >> > +} >> > +static inline u64 read_iamr(void) >> > +{ >> > + return mfspr(SPRN_IAMR); >> > +} >> > +static inline void write_iamr(u64 value) >> > +{ >> > + mtspr(SPRN_IAMR, value); >> > +} >> > +static inline u64 read_uamor(void) >> > +{ >> > + return mfspr(SPRN_UAMOR); >> > +} >> > +static inline void write_uamor(u64 value) >> > +{ >> > + mtspr(SPRN_UAMOR, value); >> > +} >> > + >> > +#else /* CONFIG_PPC64_MEMORY_PROTECTION_KEYS */ >> > + >> > +static inline u64 read_amr(void) >> > +{ >> > + WARN(1, "%s called with MEMORY PROTECTION KEYS disabled\n", __func__); >> > + return -1; >> > +} >> >> Why do we need to have a version here if we are going to WARN(), why not >> let the compilation fail if called from outside of CONFIG_PPC64_MEMORY_PROTECTION_KEYS? >> Is that the intention? > > I did not want to stop someone; kernel module for example, from calling > these interfaces from outside the pkey domain. > > Either way can be argued to be correct, I suppose. Nope, build failures are better than run time failures, otherwise the kernel will split its guts warning and warning here. Balbir Singh.