From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8E1EDC43387 for ; Tue, 8 Jan 2019 15:20:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5A45820685 for ; Tue, 8 Jan 2019 15:20:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728238AbfAHPUO (ORCPT ); Tue, 8 Jan 2019 10:20:14 -0500 Received: from foss.arm.com ([217.140.101.70]:54250 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727484AbfAHPUO (ORCPT ); Tue, 8 Jan 2019 10:20:14 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4824380D; Tue, 8 Jan 2019 07:20:13 -0800 (PST) Received: from [10.1.197.45] (e112298-lin.cambridge.arm.com [10.1.197.45]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3D5793F5AF; Tue, 8 Jan 2019 07:20:11 -0800 (PST) Subject: Re: [PATCH v8 15/26] 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, christoffer.dall@arm.com, james.morse@arm.com, catalin.marinas@arm.com, will.deacon@arm.com, mark.rutland@arm.com References: <1546956464-48825-1-git-send-email-julien.thierry@arm.com> <1546956464-48825-16-git-send-email-julien.thierry@arm.com> From: Julien Thierry Message-ID: <31a93d8b-9036-aef7-1b96-4de910a8d10b@arm.com> Date: Tue, 8 Jan 2019 15:20:09 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Suzuki, On 08/01/2019 14:51, Suzuki K Poulose wrote: > Hi Julien, > > On 08/01/2019 14:07, 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 |  1 + >>   arch/arm64/include/asm/cpufeature.h  |  4 ++++ >>   arch/arm64/kernel/alternative.c      | 43 >> +++++++++++++++++++++++++++++++----- >>   arch/arm64/kernel/cpufeature.c       |  6 +++++ >>   arch/arm64/kernel/smp.c              |  7 ++++++ >>   5 files changed, 56 insertions(+), 5 deletions(-) >> >> diff --git a/arch/arm64/include/asm/alternative.h >> b/arch/arm64/include/asm/alternative.h >> index 9806a23..b9f8d78 100644 >> --- a/arch/arm64/include/asm/alternative.h >> +++ b/arch/arm64/include/asm/alternative.h >> @@ -25,6 +25,7 @@ struct alt_instr { >>   typedef void (*alternative_cb_t)(struct alt_instr *alt, >>                    __le32 *origptr, __le32 *updptr, int nr_inst); >>   +void __init apply_boot_alternatives(void); >>   void __init apply_alternatives_all(void); >>   bool alternative_is_applied(u16 cpufeature); >>   diff --git a/arch/arm64/include/asm/cpufeature.h >> b/arch/arm64/include/asm/cpufeature.h >> index 89c3f31..e505e1f 100644 >> --- a/arch/arm64/include/asm/cpufeature.h >> +++ b/arch/arm64/include/asm/cpufeature.h >> @@ -391,6 +391,10 @@ static inline int cpucap_default_scope(const >> struct arm64_cpu_capabilities *cap) >>   extern struct static_key_false cpu_hwcap_keys[ARM64_NCAPS]; >>   extern struct static_key_false arm64_const_caps_ready; >>   +/* ARM64 CAPS + alternative_cb */ >> +#define ARM64_NPATCHABLE (ARM64_NCAPS + 1) >> +extern DECLARE_BITMAP(boot_capabilities, ARM64_NPATCHABLE); >> + >>   #define for_each_available_cap(cap)        \ >>       for_each_set_bit(cap, cpu_hwcaps, ARM64_NCAPS) >>   diff --git a/arch/arm64/kernel/alternative.c >> b/arch/arm64/kernel/alternative.c >> index c947d22..a9b4677 100644 >> --- a/arch/arm64/kernel/alternative.c >> +++ b/arch/arm64/kernel/alternative.c >> @@ -155,7 +155,8 @@ static void clean_dcache_range_nopatch(u64 start, >> u64 end) >>       } while (cur += d_size, cur < end); >>   } >>   -static void __apply_alternatives(void *alt_region, bool is_module) >> +static void __apply_alternatives(void *alt_region,  bool is_module, >> +                 unsigned long *feature_mask) >>   { >>       struct alt_instr *alt; >>       struct alt_region *region = alt_region; >> @@ -165,6 +166,9 @@ static void __apply_alternatives(void *alt_region, >> bool is_module) >>       for (alt = region->begin; alt < region->end; alt++) { >>           int nr_inst; >>   +        if (!test_bit(alt->cpufeature, feature_mask)) >> +            continue; >> + >>           /* Use ARM64_CB_PATCH as an unconditional patch */ >>           if (alt->cpufeature < ARM64_CB_PATCH && >>               !cpus_have_cap(alt->cpufeature)) >> @@ -203,8 +207,11 @@ static void __apply_alternatives(void >> *alt_region, bool is_module) >>           __flush_icache_all(); >>           isb(); >>   -        /* We applied all that was available */ >> -        bitmap_copy(applied_alternatives, cpu_hwcaps, ARM64_NCAPS); >> +        /* Ignore ARM64_CB bit from feature mask */ >> +        bitmap_or(applied_alternatives, applied_alternatives, >> +              feature_mask, ARM64_NCAPS); >> +        bitmap_and(applied_alternatives, applied_alternatives, >> +               cpu_hwcaps, ARM64_NCAPS); >>       } >>   } >>   @@ -225,8 +232,13 @@ static int __apply_alternatives_multi_stop(void >> *unused) >>               cpu_relax(); >>           isb(); >>       } else { >> +        DECLARE_BITMAP(remaining_capabilities, ARM64_NPATCHABLE); >> + >> +        bitmap_complement(remaining_capabilities, boot_capabilities, >> +                  ARM64_NPATCHABLE); >> + >>           BUG_ON(all_alternatives_applied); >> -        __apply_alternatives(®ion, false); >> +        __apply_alternatives(®ion, false, remaining_capabilities); >>           /* Barriers provided by the cache flushing */ >>           WRITE_ONCE(all_alternatives_applied, 1); >>       } >> @@ -240,6 +252,24 @@ void __init apply_alternatives_all(void) >>       stop_machine(__apply_alternatives_multi_stop, NULL, >> cpu_online_mask); >>   } >>   +/* >> + * This is called very early in the boot process (directly after we run >> + * a feature detect on the boot CPU). No need to worry about other CPUs >> + * here. >> + */ >> +void __init apply_boot_alternatives(void) >> +{ >> +    struct alt_region region = { >> +        .begin    = (struct alt_instr *)__alt_instructions, >> +        .end    = (struct alt_instr *)__alt_instructions_end, >> +    }; >> + >> +    /* If called on non-boot cpu things could go wrong */ >> +    WARN_ON(smp_processor_id() != 0); >> + >> +    __apply_alternatives(®ion, false, &boot_capabilities[0]); >> +} >> + >>   #ifdef CONFIG_MODULES >>   void apply_alternatives_module(void *start, size_t length) >>   { >> @@ -247,7 +277,10 @@ void apply_alternatives_module(void *start, >> size_t length) >>           .begin    = start, >>           .end    = start + length, >>       }; >> +    DECLARE_BITMAP(all_capabilities, ARM64_NPATCHABLE); >> + >> +    bitmap_fill(all_capabilities, ARM64_NPATCHABLE); >>   -    __apply_alternatives(®ion, true); >> +    __apply_alternatives(®ion, true, &all_capabilities[0]); >>   } >>   #endif >> diff --git a/arch/arm64/kernel/cpufeature.c >> b/arch/arm64/kernel/cpufeature.c >> index 84fa5be..71c8d4f 100644 >> --- a/arch/arm64/kernel/cpufeature.c >> +++ b/arch/arm64/kernel/cpufeature.c >> @@ -54,6 +54,9 @@ >>   EXPORT_SYMBOL(cpu_hwcaps); >>   static struct arm64_cpu_capabilities const __ro_after_init >> *cpu_hwcaps_ptrs[ARM64_NCAPS]; >>   +/* Need also bit for ARM64_CB_PATCH */ >> +DECLARE_BITMAP(boot_capabilities, ARM64_NPATCHABLE); >> + >>   /* >>    * Flag to indicate if we have computed the system wide >>    * capabilities based on the boot time active CPUs. This >> @@ -1672,6 +1675,9 @@ static void update_cpu_capabilities(u16 scope_mask) >>           if (caps->desc) >>               pr_info("detected: %s\n", caps->desc); >>           cpus_set_cap(caps->capability); >> + >> +        if (caps->type & SCOPE_BOOT_CPU) > > You may want to do : >         if (scope_mask & SCOPE_BOOT_CPU) > > for a tighter check to ensure this doesn't update the boot_capabilities > after we have applied the boot_scope alternatives and miss applying the > alternatives for those, should someone add a multi-scope (i.e > SCOPE_BOOT_CPU and > something else) capability (even by mistake). > But a multi-scope capability containing SCOPE_BOOT_CPU should already get updated for setup_boot_cpu_capabilities. Capabilities marked with SCOPE_BOOT_CPU need to be enabled on the boot CPU or not at all. Shouldn't the call to caps->matches() fail for a boot feature that was not found on the boot cpu? Also, you made the opposite suggestion 4 version ago with a more worrying scenario :) : https://lkml.org/lkml/2018/5/25/208 Otherwise, if my assumption above is wrong, it means the check should probably be: if (caps->type & SCOPE_BOOT_CPU && scope_mask & SCOPE_BOOT_CPU) But my current understanding is that we don't need that. > With that: > > Reviewed-by: Suzuki K Poulose Let me know if I can keep your tag or if I indeed need to change the condition. Thanks, -- Julien Thierry