linux-kernel - Re: [PATCH v3 3/3] KVM: VMX: Advertise PMU LBRs if and only if perf supports LBRs

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Date:   Wed, 31 Aug 2022 19:54:08 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     kernel test robot <lkp@...el.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>, kbuild-all@...ts.01.org,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, Like Xu <like.xu.linux@...il.com>
Subject: Re: [PATCH v3 3/3] KVM: VMX: Advertise PMU LBRs if and only if perf
 supports LBRs

On Wed, Aug 31, 2022, kernel test robot wrote:
> Hi Sean,
> 
> I love your patch! Yet something to improve:
> 
> [auto build test ERROR on 372d07084593dc7a399bf9bee815711b1fb1bcf2]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Sean-Christopherson/KVM-x86-Intel-LBR-related-perf-cleanups/20220831-080309
> base:   372d07084593dc7a399bf9bee815711b1fb1bcf2
> config: i386-randconfig-s001 (https://download.01.org/0day-ci/archive/20220831/202208311831.zQ4oCG1b-lkp@intel.com/config)
> compiler: gcc-11 (Debian 11.3.0-5) 11.3.0
> reproduce:
>         # apt-get install sparse
>         # sparse version: v0.6.4-39-gce1a6720-dirty
>         # https://github.com/intel-lab-lkp/linux/commit/094f42374997562fff3f9f9637ec9aa8257490a0
>         git remote add linux-review https://github.com/intel-lab-lkp/linux
>         git fetch --no-tags linux-review Sean-Christopherson/KVM-x86-Intel-LBR-related-perf-cleanups/20220831-080309
>         git checkout 094f42374997562fff3f9f9637ec9aa8257490a0
>         # save the config file
>         mkdir build_dir && cp config build_dir/.config
>         make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=i386 prepare
> 
> If you fix the issue, kindly add following tag where applicable
> Reported-by: kernel test robot <lkp@...el.com>
> 
> All errors (new ones prefixed by >>):
> 
>    In file included from arch/x86/kernel/../kvm/vmx/vmx.h:11,
>                     from arch/x86/kernel/asm-offsets.c:22:

Argh, KVM's "internal" vmx.h gets included by arch/x86/kernel/asm-offsets.c even
when KVM is disabled, and vmx_get_perf_capabilities() is oddly inlined there.

The simple fix is to move the definition of vmx_get_perf_capabilities() into vmx.c.

Long term, I want to figure out a way to break the dependency on asm-offsets.  I
ran afoul of this a week ago for something else, but couldn't figure an easy
solution and it wasn't (yet) a blocking issue.