linux-kernel - Re: [PATCH v3 08/16] perf: Force architectures to opt-in to guest callbacks

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Message-ID: <YYsIR/yEYm2nAz/p@google.com>
Date:   Tue, 9 Nov 2021 23:46:15 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Marc Zyngier <maz@...nel.org>, Guo Ren <guoren@...nel.org>,
        Nick Hu <nickhu@...estech.com>,
        Greentime Hu <green.hu@...il.com>,
        Vincent Chen <deanbo422@...il.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Stefano Stabellini <sstabellini@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu, linux-csky@...r.kernel.org,
        linux-riscv@...ts.infradead.org, kvm@...r.kernel.org,
        xen-devel@...ts.xenproject.org,
        Artem Kashkanov <artem.kashkanov@...el.com>,
        Like Xu <like.xu.linux@...il.com>,
        Zhu Lingshan <lingshan.zhu@...el.com>
Subject: Re: [PATCH v3 08/16] perf: Force architectures to opt-in to guest
 callbacks

On Wed, Sep 22, 2021, Sean Christopherson wrote:
> On Wed, Sep 22, 2021, Paolo Bonzini wrote:
> > On 22/09/21 02:05, Sean Christopherson wrote:
> > > @@ -1273,6 +1274,11 @@ static inline unsigned int perf_guest_handle_intel_pt_intr(void)
> > >   }
> > >   extern void perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *cbs);
> > >   extern void perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs);
> > > +#else
> > > +static inline unsigned int perf_guest_state(void)		 { return 0; }
> > > +static inline unsigned long perf_guest_get_ip(void)		 { return 0; }
> > > +static inline unsigned int perf_guest_handle_intel_pt_intr(void) { return 0; }
> > > +#endif /* CONFIG_GUEST_PERF_EVENTS */
> > 
> > Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>
> > 
> > Having perf_guest_handle_intel_pt_intr in generic code is a bit off.  Of
> > course it has to be in the struct, but the wrapper might be placed in
> > arch/x86/include/asm/perf_event.h as well (applies to patch 7 as well).
> 
> Yeah, I went with this option purely to keep everything bundled together.  I have
> no strong opinion.

Scratch, that, I do have an opinion.  perf_guest_handle_intel_pt_intr() is in
common code because the callbacks themselves and perf_get_guest_cbs() are defined
in linux/perf_event.h, _after_ asm/perf_event.h is included.

arch/x86/include/asm/perf_event.h is quite bereft of includes, so there's no
obvious landing spot for those two things, and adding a new header seems like
overkill.