linux-kernel - Re: [PATCH 0/5] KVM: x86: Use kernel x86 cpuid utilities in KVM selftests

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Message-ID: <YIm7iWxggvoN9riz@google.com>
Date:   Wed, 28 Apr 2021 12:46:17 -0700
From:   Ricardo Koller <ricarkol@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH 0/5] KVM: x86: Use kernel x86 cpuid utilities in KVM
 selftests

On Thu, Apr 22, 2021 at 09:02:09AM +0200, Paolo Bonzini wrote:
> On 22/04/21 02:56, Ricardo Koller wrote:
> > The kernel has a set of utilities and definitions to deal with x86 cpu
> > features.  The x86 KVM selftests don't use them, and instead have
> > evolved to use differing and ad-hoc methods for checking features. The
> > advantage of the kernel feature definitions is that they use a format
> > that embeds the info needed to extract them from cpuid (function, index,
> > and register to use).
> > 
> > The first 3 patches massage the related cpuid header files in the kernel
> > side, then copy them into tools/ so they can be included by selftests.
> > The last 2 patches replace the tests checking for cpu features to use
> > the definitions and utilities introduced from the kernel.
> 
> I queued the first, but I am not sure about the rest.
> 
> An alternative is to copy over the code from kvm-unit-tests which encodes
> the leaf/subleaf/register/bit values into the X86_FEATURE_* value.  Sharing
> code with kvm-unit-tests is probably simpler than adding #ifdef __KERNEL__
> and keeping the headers in sync.
> 
> Paolo
> 

Thanks. I was thinking about kvm-unit-tests, but the issue is that it
would also be a copy. And just like with kernel headers, it would be
ideal to keep them in-sync. The advantage of the kernel headers is that
it's much easier to check and fix diffs with them. On the other hand, as
you say, there would not be any #ifdef stuff with kvm=unit-tests. Please
let me know what you think. 

Thanks,
Ricardo

> > Thanks,
> > Ricardo
> > 
> > Ricardo Koller (5):
> >    KVM: x86: Move reverse CPUID helpers to separate header file
> >    x86/cpu: Expose CPUID regs, leaf and index definitions to tools
> >    tools headers x86: Copy cpuid helpers from the kernel
> >    KVM: selftests: Introduce utilities for checking x86 features
> >    KVM: selftests: Use kernel x86 cpuid features format
> > 
> >   arch/x86/events/intel/pt.c                    |   1 +
> >   arch/x86/include/asm/cpufeature.h             |  23 +-
> >   arch/x86/include/asm/processor.h              |  11 -
> >   arch/x86/kernel/cpu/scattered.c               |   2 +-
> >   arch/x86/kernel/cpuid.c                       |   2 +-
> >   arch/x86/kvm/cpuid.h                          | 177 +-----------
> >   arch/x86/kvm/reverse_cpuid.h                  | 185 +++++++++++++
> >   tools/arch/x86/include/asm/cpufeature.h       | 257 ++++++++++++++++++
> >   tools/arch/x86/include/asm/cpufeatures.h      |   3 +
> >   .../selftests/kvm/include/x86_64/cpuid.h      |  61 +++++
> >   .../selftests/kvm/include/x86_64/processor.h  |  16 --
> >   .../kvm/include/x86_64/reverse_cpuid.h        | 185 +++++++++++++
> >   .../selftests/kvm/include/x86_64/svm_util.h   |  11 +-
> >   tools/testing/selftests/kvm/lib/x86_64/svm.c  |   6 +-
> >   tools/testing/selftests/kvm/lib/x86_64/vmx.c  |   5 +-
> >   tools/testing/selftests/kvm/steal_time.c      |   5 +-
> >   .../kvm/x86_64/cr4_cpuid_sync_test.c          |  23 +-
> >   .../selftests/kvm/x86_64/set_sregs_test.c     |  25 +-
> >   .../selftests/kvm/x86_64/vmx_pmu_msrs_test.c  |   8 +-
> >   .../kvm/x86_64/vmx_set_nested_state_test.c    |   5 +-
> >   .../selftests/kvm/x86_64/xss_msr_test.c       |  10 +-
> >   21 files changed, 749 insertions(+), 272 deletions(-)
> >   create mode 100644 arch/x86/kvm/reverse_cpuid.h
> >   create mode 100644 tools/arch/x86/include/asm/cpufeature.h
> >   create mode 100644 tools/testing/selftests/kvm/include/x86_64/cpuid.h
> >   create mode 100644 tools/testing/selftests/kvm/include/x86_64/reverse_cpuid.h
> > 
>