From mboxrd@z Thu Jan 1 00:00:00 1970 From: Suzuki.Poulose@arm.com (Suzuki K Poulose) Date: Fri, 25 May 2018 11:00:58 +0100 Subject: [PATCH v4 04/26] arm64: alternative: Apply alternatives early in boot process In-Reply-To: <1527241772-48007-5-git-send-email-julien.thierry@arm.com> References: <1527241772-48007-1-git-send-email-julien.thierry@arm.com> <1527241772-48007-5-git-send-email-julien.thierry@arm.com> Message-ID: <89769f8d-2ed0-1eb7-0373-09fc25f8071a@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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. Suzuki From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965553AbeEYKBD (ORCPT ); Fri, 25 May 2018 06:01:03 -0400 Received: from foss.arm.com ([217.140.101.70]:58158 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965291AbeEYKBC (ORCPT ); Fri, 25 May 2018 06:01:02 -0400 Subject: Re: [PATCH v4 04/26] arm64: alternative: Apply alternatives early in boot process To: Julien Thierry , 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> From: Suzuki K Poulose Message-ID: <89769f8d-2ed0-1eb7-0373-09fc25f8071a@arm.com> Date: Fri, 25 May 2018 11:00:58 +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: <1527241772-48007-5-git-send-email-julien.thierry@arm.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Suzuki