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[35.185.214.157]) by smtp.gmail.com with ESMTPSA id 27sm18661619pgx.81.2021.12.29.17.18.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Dec 2021 17:18:05 -0800 (PST) Date: Thu, 30 Dec 2021 01:18:02 +0000 From: Sean Christopherson To: kernel test robot Cc: Tom Lendacky , kbuild-all@lists.01.org, linux-kernel@vger.kernel.org, Paolo Bonzini Subject: Re: vmlinux.o: warning: objtool: __svm_sev_es_vcpu_run()+0x54: BP used as a scratch register Message-ID: References: <202111172015.2zvJUEBY-lkp@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202111172015.2zvJUEBY-lkp@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 17, 2021, kernel test robot wrote: > tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master > head: 8ab774587903771821b59471cc723bba6d893942 > commit: 16809ecdc1e8ab7278f1d60021ac809edd17d060 KVM: SVM: Provide an updated VMRUN invocation for SEV-ES guests > date: 11 months ago > config: x86_64-buildonly-randconfig-r005-20211117 (attached as .config) > compiler: gcc-9 (Debian 9.3.0-22) 9.3.0 > reproduce (this is a W=1 build): > # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=16809ecdc1e8ab7278f1d60021ac809edd17d060 > git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git > git fetch --no-tags linus master > git checkout 16809ecdc1e8ab7278f1d60021ac809edd17d060 > # save the attached .config to linux build tree > mkdir build_dir > make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash > > If you fix the issue, kindly add following tag as appropriate > Reported-by: kernel test robot > > All warnings (new ones prefixed by >>): > > vmlinux.o: warning: objtool: __do_fast_syscall_32()+0x3d: call to syscall_enter_from_user_mode_work() leaves .noinstr.text section > vmlinux.o: warning: objtool: __svm_vcpu_run()+0x10e: BP used as a scratch register > >> vmlinux.o: warning: objtool: __svm_sev_es_vcpu_run()+0x54: BP used as a scratch register __svm_vcpu_run() and __svm_sev_es_vcpu_run() PUSH/POP RBP but don't create a stack frame, which triggers the objtool warning because objtool things the code is using BP as a scratch register (obviously). This shows up when CONFIG_FRAME_POINTER=y and KVM AMD is built into the kernel (apparently 'objtool check' isn't run on modules?). The easy fix to is add "mov %rsp, %rbp" to create a stack frame. Kinda pointless since neither function makes true calls to other functions, but the extra MOV is harmless and it'd be nice to get rid of the objtool warning.