From: Sean Christopherson <seanjc@google.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Wanpeng Li <wanpengli@tencent.com>,
kvm@vger.kernel.org,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Guo Ren <guoren@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
linux-riscv@lists.infradead.org,
Vincent Chen <deanbo422@gmail.com>, Jiri Olsa <jolsa@redhat.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Stefano Stabellini <sstabellini@kernel.org>,
xen-devel@lists.xenproject.org, Marc Zyngier <maz@kernel.org>,
Joerg Roedel <joro@8bytes.org>,
x86@kernel.org, linux-csky@vger.kernel.org,
kvmarm@lists.cs.columbia.edu, Ingo Molnar <mingo@redhat.com>,
Like Xu <like.xu.linux@gmail.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Zhu Lingshan <lingshan.zhu@intel.com>,
Will Deacon <will@kernel.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Borislav Petkov <bp@alien8.de>, Greentime Hu <green.hu@gmail.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Namhyung Kim <namhyung@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Artem Kashkanov <artem.kashkanov@intel.com>,
linux-arm-kernel@lists.infradead.org,
Jim Mattson <jmattson@google.com>,
Juergen Gross <jgross@suse.com>, Nick Hu <nickhu@andestech.com>,
linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
Palmer Dabbelt <palmer@dabbelt.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>
Subject: Re: [PATCH v2 01/13] perf: Ensure perf_guest_cbs aren't reloaded between !NULL check and deref
Date: Thu, 16 Sep 2021 21:41:01 +0000 [thread overview]
Message-ID: <YUO57TlEGlUk2Q03@google.com> (raw)
In-Reply-To: <20210828194421.GB4353@worktop.programming.kicks-ass.net>
On Sat, Aug 28, 2021, Peter Zijlstra wrote:
> On Fri, Aug 27, 2021 at 05:35:46PM -0700, Sean Christopherson wrote:
> > diff --git a/kernel/events/core.c b/kernel/events/core.c
> > index 464917096e73..2126f6327321 100644
> > --- a/kernel/events/core.c
> > +++ b/kernel/events/core.c
> > @@ -6491,14 +6491,19 @@ struct perf_guest_info_callbacks *perf_guest_cbs;
> >
> > int perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
> > {
> > - perf_guest_cbs = cbs;
> > + if (WARN_ON_ONCE(perf_guest_cbs))
> > + return -EBUSY;
> > +
> > + WRITE_ONCE(perf_guest_cbs, cbs);
> > + synchronize_rcu();
>
> You're waiting for all NULL users to go away? :-) IOW, we can do without
> this synchronize_rcu() call.
Doh, right. I was thinking KVM needed to wait for in-progress NMI to exit to
ensure guest PT interrupts are handled correctly, but obviously the NMI handler
needs to exit for that CPU to get into a guest...
> > return 0;
> > }
> > EXPORT_SYMBOL_GPL(perf_register_guest_info_callbacks);
> >
> > int perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
> > {
> > - perf_guest_cbs = NULL;
>
> if (WARN_ON_ONCE(perf_guest_cbs != cbs))
> return -EBUSY;
>
> ?
Works for me. I guess I'm more optimistic about people not being morons :-)
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next prev parent reply other threads:[~2021-09-17 8:46 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-28 0:35 [PATCH v2 00/13] perf: KVM: Fix, optimize, and clean up callbacks Sean Christopherson
2021-08-28 0:35 ` [PATCH v2 01/13] perf: Ensure perf_guest_cbs aren't reloaded between !NULL check and deref Sean Christopherson
2021-08-28 19:44 ` Peter Zijlstra
2021-09-16 21:41 ` Sean Christopherson [this message]
2021-08-28 0:35 ` [PATCH v2 02/13] KVM: x86: Register perf callbacks after calling vendor's hardware_setup() Sean Christopherson
2021-08-28 0:35 ` [PATCH v2 03/13] KVM: x86: Register Processor Trace interrupt hook iff PT enabled in guest Sean Christopherson
2021-08-28 0:35 ` [PATCH v2 04/13] perf: Stop pretending that perf can handle multiple guest callbacks Sean Christopherson
2021-08-28 0:35 ` [PATCH v2 05/13] perf: Force architectures to opt-in to " Sean Christopherson
2021-08-28 19:47 ` Peter Zijlstra
2021-09-16 22:30 ` Sean Christopherson
2021-09-21 16:44 ` Paolo Bonzini
2021-09-21 21:29 ` Sean Christopherson
2021-08-28 0:35 ` [PATCH v2 06/13] perf/core: Rework guest callbacks to prepare for static_call support Sean Christopherson
2021-08-28 0:35 ` [PATCH v2 07/13] perf/core: Use static_call to optimize perf_guest_info_callbacks Sean Christopherson
2021-08-28 0:35 ` [PATCH v2 08/13] KVM: x86: Drop current_vcpu for kvm_running_vcpu + kvm_arch_vcpu variable Sean Christopherson
2021-08-28 0:35 ` [PATCH v2 09/13] KVM: x86: More precisely identify NMI from guest when handling PMI Sean Christopherson
2021-08-28 0:35 ` [PATCH v2 10/13] KVM: Move x86's perf guest info callbacks to generic KVM Sean Christopherson
2021-08-28 0:35 ` [PATCH v2 11/13] KVM: x86: Move Intel Processor Trace interrupt handler to vmx.c Sean Christopherson
2021-08-28 0:35 ` [PATCH v2 12/13] KVM: arm64: Convert to the generic perf callbacks Sean Christopherson
2021-08-28 0:35 ` [PATCH v2 13/13] KVM: arm64: Drop perf.c and fold its tiny bits of code into arm.c / pmu.c Sean Christopherson
2021-08-28 20:13 ` [PATCH v2 00/13] perf: KVM: Fix, optimize, and clean up callbacks Peter Zijlstra
2021-09-16 21:37 ` Sean Christopherson
2021-09-17 7:28 ` Peter Zijlstra
2021-09-17 16:53 ` Sean Christopherson
2021-09-20 12:05 ` Paolo Bonzini
2021-09-20 12:22 ` Marc Zyngier
2021-09-20 13:18 ` Paolo Bonzini
2021-09-20 13:40 ` Marc Zyngier
2021-09-20 18:22 ` Paolo Bonzini
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