From mboxrd@z Thu Jan 1 00:00:00 1970 From: julien.thierry@arm.com (Julien Thierry) Date: Fri, 25 May 2018 11:25:34 +0100 Subject: [PATCH v4 04/26] arm64: alternative: Apply alternatives early in boot process In-Reply-To: <89769f8d-2ed0-1eb7-0373-09fc25f8071a@arm.com> References: <1527241772-48007-1-git-send-email-julien.thierry@arm.com> <1527241772-48007-5-git-send-email-julien.thierry@arm.com> <89769f8d-2ed0-1eb7-0373-09fc25f8071a@arm.com> Message-ID: <7e579de3-cab2-0677-a3d0-d150ee72f839@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 25/05/18 11:00, Suzuki K Poulose wrote: > On 25/05/18 10:49, Julien Thierry wrote: >> From: Daniel Thompson >> >> Currently alternatives are applied very late in the boot process (and >> a long time after we enable scheduling). Some alternative sequences, >> such as those that alter the way CPU context is stored, must be applied >> much earlier in the boot sequence. >> >> Introduce apply_boot_alternatives() to allow some alternatives to be >> applied immediately after we detect the CPU features of the boot CPU. >> >> Signed-off-by: Daniel Thompson >> [julien.thierry at arm.com: rename to fit new cpufeature framework better, >> ???????????? apply BOOT_SCOPE feature early in boot] >> Signed-off-by: Julien Thierry >> Cc: Catalin Marinas >> Cc: Will Deacon >> Cc: Christoffer Dall >> Cc: Suzuki K Poulose >> --- >> ? arch/arm64/include/asm/alternative.h |? 3 +-- >> ? arch/arm64/include/asm/cpufeature.h? |? 2 ++ >> ? arch/arm64/kernel/alternative.c????? | 30 >> +++++++++++++++++++++++++++--- >> ? arch/arm64/kernel/cpufeature.c?????? |? 5 +++++ >> ? arch/arm64/kernel/smp.c????????????? |? 7 +++++++ >> ? 5 files changed, 42 insertions(+), 5 deletions(-) >> > > ... > >> +unsigned long boot_capabilities; >> + >> ? /* >> ?? * Flag to indicate if we have computed the system wide >> ?? * capabilities based on the boot time active CPUs. This >> @@ -1370,6 +1372,9 @@ static void __update_cpu_capabilities(const >> struct arm64_cpu_capabilities *caps, >> ????????? if (!cpus_have_cap(caps->capability) && caps->desc) >> ????????????? pr_info("%s %s\n", info, caps->desc); >> ????????? cpus_set_cap(caps->capability); >> + >> +??????? if (scope_mask & SCOPE_BOOT_CPU) >> +??????????? __set_bit(caps->capability, &boot_capabilities); > > Julien > > I think this check is problematic. The scope_mask passed on by the boot CPU > is (SCOPE_BOOT_CPU | SCOPE_LOCAL_CPU) to cover both BOOT CPU > capabilities *and* > CPU local capabilites on the boot CPU. So, you might apply the > alternatives for > a "local" CPU erratum, which is not intended. You may change the above > check to : > > ????if (caps->type & SCOPE_BOOT_CPU) > > to make sure you check the "capability" has the SCOPE_BOOT_CPU set. > Makes sense, I'll do that. Thanks, -- Julien Thierry From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965898AbeEYKZj (ORCPT ); Fri, 25 May 2018 06:25:39 -0400 Received: from foss.arm.com ([217.140.101.70]:58828 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965102AbeEYKZi (ORCPT ); Fri, 25 May 2018 06:25:38 -0400 Subject: Re: [PATCH v4 04/26] arm64: alternative: Apply alternatives early in boot process To: Suzuki K Poulose , linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, daniel.thompson@linaro.org, joel@joelfernandes.org, marc.zyngier@arm.com, mark.rutland@arm.com, christoffer.dall@arm.com, james.morse@arm.com, catalin.marinas@arm.com, will.deacon@arm.com, Christoffer Dall References: <1527241772-48007-1-git-send-email-julien.thierry@arm.com> <1527241772-48007-5-git-send-email-julien.thierry@arm.com> <89769f8d-2ed0-1eb7-0373-09fc25f8071a@arm.com> From: Julien Thierry Message-ID: <7e579de3-cab2-0677-a3d0-d150ee72f839@arm.com> Date: Fri, 25 May 2018 11:25:34 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <89769f8d-2ed0-1eb7-0373-09fc25f8071a@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 25/05/18 11:00, Suzuki K Poulose wrote: > On 25/05/18 10:49, Julien Thierry wrote: >> From: Daniel Thompson >> >> Currently alternatives are applied very late in the boot process (and >> a long time after we enable scheduling). Some alternative sequences, >> such as those that alter the way CPU context is stored, must be applied >> much earlier in the boot sequence. >> >> Introduce apply_boot_alternatives() to allow some alternatives to be >> applied immediately after we detect the CPU features of the boot CPU. >> >> Signed-off-by: Daniel Thompson >> [julien.thierry@arm.com: rename to fit new cpufeature framework better, >>              apply BOOT_SCOPE feature early in boot] >> Signed-off-by: Julien Thierry >> Cc: Catalin Marinas >> Cc: Will Deacon >> Cc: Christoffer Dall >> Cc: Suzuki K Poulose >> --- >>   arch/arm64/include/asm/alternative.h |  3 +-- >>   arch/arm64/include/asm/cpufeature.h  |  2 ++ >>   arch/arm64/kernel/alternative.c      | 30 >> +++++++++++++++++++++++++++--- >>   arch/arm64/kernel/cpufeature.c       |  5 +++++ >>   arch/arm64/kernel/smp.c              |  7 +++++++ >>   5 files changed, 42 insertions(+), 5 deletions(-) >> > > ... > >> +unsigned long boot_capabilities; >> + >>   /* >>    * Flag to indicate if we have computed the system wide >>    * capabilities based on the boot time active CPUs. This >> @@ -1370,6 +1372,9 @@ static void __update_cpu_capabilities(const >> struct arm64_cpu_capabilities *caps, >>           if (!cpus_have_cap(caps->capability) && caps->desc) >>               pr_info("%s %s\n", info, caps->desc); >>           cpus_set_cap(caps->capability); >> + >> +        if (scope_mask & SCOPE_BOOT_CPU) >> +            __set_bit(caps->capability, &boot_capabilities); > > Julien > > I think this check is problematic. The scope_mask passed on by the boot CPU > is (SCOPE_BOOT_CPU | SCOPE_LOCAL_CPU) to cover both BOOT CPU > capabilities *and* > CPU local capabilites on the boot CPU. So, you might apply the > alternatives for > a "local" CPU erratum, which is not intended. You may change the above > check to : > >     if (caps->type & SCOPE_BOOT_CPU) > > to make sure you check the "capability" has the SCOPE_BOOT_CPU set. > Makes sense, I'll do that. Thanks, -- Julien Thierry