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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 F165DC433DB for ; Tue, 9 Mar 2021 09:59:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C3FD96518F for ; Tue, 9 Mar 2021 09:59:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229916AbhCIJ6g (ORCPT ); Tue, 9 Mar 2021 04:58:36 -0500 Received: from pegase1.c-s.fr ([93.17.236.30]:31735 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229480AbhCIJ6C (ORCPT ); Tue, 9 Mar 2021 04:58:02 -0500 Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 4DvrHW3Jcrz9txfL; Tue, 9 Mar 2021 10:57:59 +0100 (CET) X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id J6axhznGM18g; Tue, 9 Mar 2021 10:57:59 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 4DvrHW1tYWz9txfN; Tue, 9 Mar 2021 10:57:59 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 6DDA68B7E7; Tue, 9 Mar 2021 10:58:00 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id ES4Klg5zpPJo; Tue, 9 Mar 2021 10:58:00 +0100 (CET) Received: from [192.168.4.90] (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id C48CB8B7DC; Tue, 9 Mar 2021 10:57:59 +0100 (CET) Subject: Re: [PATCH] powerpc: Fix missing declaration of [en/dis]able_kernel_vsx() To: Geert Uytterhoeven Cc: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Linux Kernel Mailing List , linuxppc-dev , amd-gfx list , =?UTF-8?Q?Christian_K=c3=b6nig?= , Alex Deucher References: <8d7d285a027e9d21f5ff7f850fa71a2655b0c4af.1615279170.git.christophe.leroy@csgroup.eu> From: Christophe Leroy Message-ID: Date: Tue, 9 Mar 2021 10:57:44 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le 09/03/2021 à 10:16, Geert Uytterhoeven a écrit : > Hi Christophe, > > On Tue, Mar 9, 2021 at 9:52 AM Christophe Leroy > wrote: >> Le 09/03/2021 à 09:45, Geert Uytterhoeven a écrit : >>> On Tue, Mar 9, 2021 at 9:39 AM Christophe Leroy >>> wrote: >>>> Add stub instances of enable_kernel_vsx() and disable_kernel_vsx() >>>> when CONFIG_VSX is not set, to avoid following build failure. >>>> >>>> CC [M] drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dcn_calcs.o >>>> In file included from ./drivers/gpu/drm/amd/amdgpu/../display/dc/dm_services_types.h:29, >>>> from ./drivers/gpu/drm/amd/amdgpu/../display/dc/dm_services.h:37, >>>> from drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dcn_calcs.c:27: >>>> drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dcn_calcs.c: In function 'dcn_bw_apply_registry_override': >>>> ./drivers/gpu/drm/amd/amdgpu/../display/dc/os_types.h:64:3: error: implicit declaration of function 'enable_kernel_vsx'; did you mean 'enable_kernel_fp'? [-Werror=implicit-function-declaration] >>>> 64 | enable_kernel_vsx(); \ >>>> | ^~~~~~~~~~~~~~~~~ >>>> drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dcn_calcs.c:640:2: note: in expansion of macro 'DC_FP_START' >>>> 640 | DC_FP_START(); >>>> | ^~~~~~~~~~~ >>>> ./drivers/gpu/drm/amd/amdgpu/../display/dc/os_types.h:75:3: error: implicit declaration of function 'disable_kernel_vsx'; did you mean 'disable_kernel_fp'? [-Werror=implicit-function-declaration] >>>> 75 | disable_kernel_vsx(); \ >>>> | ^~~~~~~~~~~~~~~~~~ >>>> drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dcn_calcs.c:676:2: note: in expansion of macro 'DC_FP_END' >>>> 676 | DC_FP_END(); >>>> | ^~~~~~~~~ >>>> cc1: some warnings being treated as errors >>>> make[5]: *** [drivers/gpu/drm/amd/amdgpu/../display/dc/calcs/dcn_calcs.o] Error 1 >>>> >>>> Fixes: 16a9dea110a6 ("amdgpu: Enable initial DCN support on POWER") >>>> Cc: stable@vger.kernel.org >>>> Signed-off-by: Christophe Leroy >>> >>> Thanks for your patch! >>> >>>> --- a/arch/powerpc/include/asm/switch_to.h >>>> +++ b/arch/powerpc/include/asm/switch_to.h >>>> @@ -71,6 +71,16 @@ static inline void disable_kernel_vsx(void) >>>> { >>>> msr_check_and_clear(MSR_FP|MSR_VEC|MSR_VSX); >>>> } >>>> +#else >>>> +static inline void enable_kernel_vsx(void) >>>> +{ >>>> + BUILD_BUG(); >>>> +} >>>> + >>>> +static inline void disable_kernel_vsx(void) >>>> +{ >>>> + BUILD_BUG(); >>>> +} >>>> #endif >>> >>> I'm wondering how this is any better than the current situation: using >>> BUILD_BUG() will still cause a build failure? >> >> No it won't cause a failure. In drivers/gpu/drm/amd/display/dc/os_types.h you have: >> >> #define DC_FP_START() { \ >> if (cpu_has_feature(CPU_FTR_VSX_COMP)) { \ >> preempt_disable(); \ >> enable_kernel_vsx(); \ >> } else if (cpu_has_feature(CPU_FTR_ALTIVEC_COMP)) { \ >> preempt_disable(); \ >> enable_kernel_altivec(); \ >> } else if (!cpu_has_feature(CPU_FTR_FPU_UNAVAILABLE)) { \ >> preempt_disable(); \ >> enable_kernel_fp(); \ >> } \ >> >> When CONFIG_VSX is not selected, cpu_has_feature(CPU_FTR_VSX_COMP) constant folds to 'false' so the >> call to enable_kernel_vsx() is discarded and the build succeeds. > > IC. So you might as well have an empty (dummy) function instead? > But with an empty function, you take the risk that one day, someone calls it without checking that CONFIG_VSX is selected. Here if someone does that, build will fail. Another solution is to declare a non static prototype of it, like __put_user_bad() for instance. In that case, the link will fail. I prefer the BUILD_BUG() approach as I find it cleaner and more explicit, and also because it breaks the build at compile time, you don't have to wait link time to catch the error. Christophe