From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thiago Jung Bauermann Subject: Re: [RFC v6 20/62] powerpc: store and restore the pkey state across context switches Date: Thu, 27 Jul 2017 14:32:59 -0300 Message-ID: <878tj94wfo.fsf@linux.vnet.ibm.com> References: <1500177424-13695-1-git-send-email-linuxram@us.ibm.com> <1500177424-13695-21-git-send-email-linuxram@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:48526 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751518AbdG0RdQ (ORCPT ); Thu, 27 Jul 2017 13:33:16 -0400 Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v6RHSZJv068328 for ; Thu, 27 Jul 2017 13:33:15 -0400 Received: from e24smtp01.br.ibm.com (e24smtp01.br.ibm.com [32.104.18.85]) by mx0b-001b2d01.pphosted.com with ESMTP id 2byjfueb0u-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 27 Jul 2017 13:33:15 -0400 Received: from localhost by e24smtp01.br.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 27 Jul 2017 14:33:13 -0300 In-reply-to: <1500177424-13695-21-git-send-email-linuxram@us.ibm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Ram Pai Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, arnd@arndb.de, corbet@lwn.net, mhocko@kernel.org, dave.hansen@intel.com, mingo@redhat.com, paulus@samba.org, aneesh.kumar@linux.vnet.ibm.com, akpm@linux-foundation.org, khandual@linux.vnet.ibm.com Ram Pai writes: > Store and restore the AMR, IAMR and UMOR register state of the task > before scheduling out and after scheduling in, respectively. > > Signed-off-by: Ram Pai s/UMOR/UAMOR/ > diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c > index 2ad725e..9429361 100644 > --- a/arch/powerpc/kernel/process.c > +++ b/arch/powerpc/kernel/process.c > @@ -1096,6 +1096,11 @@ static inline void save_sprs(struct thread_struct *t) > t->tar = mfspr(SPRN_TAR); > } > #endif > +#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS > + t->amr = mfspr(SPRN_AMR); > + t->iamr = mfspr(SPRN_IAMR); > + t->uamor = mfspr(SPRN_UAMOR); > +#endif > } > > static inline void restore_sprs(struct thread_struct *old_thread, > @@ -1131,6 +1136,14 @@ static inline void restore_sprs(struct thread_struct *old_thread, > mtspr(SPRN_TAR, new_thread->tar); > } > #endif > +#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS > + if (old_thread->amr != new_thread->amr) > + mtspr(SPRN_AMR, new_thread->amr); > + if (old_thread->iamr != new_thread->iamr) > + mtspr(SPRN_IAMR, new_thread->iamr); > + if (old_thread->uamor != new_thread->uamor) > + mtspr(SPRN_UAMOR, new_thread->uamor); > +#endif > } Shouldn't the saving and restoring of the SPRs be guarded by a check for whether memory protection keys are enabled? What happens when trying to access these registers on a CPU which doesn't have them? -- Thiago Jung Bauermann IBM Linux Technology Center