Re: [PATCH v3 01/16] perf: Ensure perf_guest_cbs aren't reloaded between... | linux-arm-kernel

[PATCH v3 00/16] perf: KVM: Fix, optimize, and clean up callbacks · Sean Christopherson <seanjc@google.com> · 2021-09-22
[PATCH v3 01/16] perf: Ensure perf_guest_cbs aren't reloaded between !NULL check and deref · Sean Christopherson <seanjc@google.com> · 2021-09-22
Re: [PATCH v3 01/16] perf: Ensure perf_guest_cbs aren't reloaded between !NULL check and deref · Like Xu <hidden> · 2021-11-04
Re: [PATCH v3 01/16] perf: Ensure perf_guest_cbs aren't reloaded between !NULL check and deref · Sean Christopherson <seanjc@google.com> · 2021-11-04
Re: [PATCH v3 01/16] perf: Ensure perf_guest_cbs aren't reloaded between !NULL check and deref · Paolo Bonzini <pbonzini@redhat.com> · 2021-11-10
Re: [PATCH v3 01/16] perf: Ensure perf_guest_cbs aren't reloaded between !NULL check and deref · Sean Christopherson <seanjc@google.com> · 2021-11-11
[PATCH v3 02/16] KVM: x86: Register perf callbacks after calling vendor's hardware_setup() · Sean Christopherson <seanjc@google.com> · 2021-09-22
Re: [PATCH v3 02/16] KVM: x86: Register perf callbacks after calling vendor's hardware_setup() · Paolo Bonzini <pbonzini@redhat.com> · 2021-09-22
[PATCH v3 03/16] KVM: x86: Register Processor Trace interrupt hook iff PT enabled in guest · Sean Christopherson <seanjc@google.com> · 2021-09-22
Re: [PATCH v3 03/16] KVM: x86: Register Processor Trace interrupt hook iff PT enabled in guest · Paolo Bonzini <pbonzini@redhat.com> · 2021-09-22
[PATCH v3 04/16] perf: Stop pretending that perf can handle multiple guest callbacks · Sean Christopherson <seanjc@google.com> · 2021-09-22
Re: [PATCH v3 04/16] perf: Stop pretending that perf can handle multiple guest callbacks · Paolo Bonzini <pbonzini@redhat.com> · 2021-09-22
[PATCH v3 05/16] perf: Drop dead and useless guest "support" from arm, csky, nds32 and riscv · Sean Christopherson <seanjc@google.com> · 2021-09-22
Re: [PATCH v3 05/16] perf: Drop dead and useless guest "support" from arm, csky, nds32 and riscv · Paolo Bonzini <pbonzini@redhat.com> · 2021-09-22
[PATCH v3 06/16] perf/core: Rework guest callbacks to prepare for static_call support · Sean Christopherson <seanjc@google.com> · 2021-09-22
Re: [PATCH v3 06/16] perf/core: Rework guest callbacks to prepare for static_call support · Paolo Bonzini <pbonzini@redhat.com> · 2021-09-22
Re: [PATCH v3 06/16] perf/core: Rework guest callbacks to prepare for static_call support · Boris Ostrovsky <boris.ostrovsky@oracle.com> · 2021-09-22
[PATCH v3 07/16] perf: Add wrappers for invoking guest callbacks · Sean Christopherson <seanjc@google.com> · 2021-09-22
Re: [PATCH v3 07/16] perf: Add wrappers for invoking guest callbacks · Paolo Bonzini <pbonzini@redhat.com> · 2021-09-22
[PATCH v3 08/16] perf: Force architectures to opt-in to guest callbacks · Sean Christopherson <seanjc@google.com> · 2021-09-22
Re: [PATCH v3 08/16] perf: Force architectures to opt-in to guest callbacks · Paolo Bonzini <pbonzini@redhat.com> · 2021-09-22
Re: [PATCH v3 08/16] perf: Force architectures to opt-in to guest callbacks · Sean Christopherson <seanjc@google.com> · 2021-09-22
Re: [PATCH v3 08/16] perf: Force architectures to opt-in to guest callbacks · Sean Christopherson <seanjc@google.com> · 2021-11-09
[PATCH v3 09/16] perf/core: Use static_call to optimize perf_guest_info_callbacks · Sean Christopherson <seanjc@google.com> · 2021-09-22
Re: [PATCH v3 09/16] perf/core: Use static_call to optimize perf_guest_info_callbacks · Paolo Bonzini <pbonzini@redhat.com> · 2021-09-22
[PATCH v3 10/16] KVM: x86: Drop current_vcpu for kvm_running_vcpu + kvm_arch_vcpu variable · Sean Christopherson <seanjc@google.com> · 2021-09-22
Re: [PATCH v3 10/16] KVM: x86: Drop current_vcpu for kvm_running_vcpu + kvm_arch_vcpu variable · Paolo Bonzini <pbonzini@redhat.com> · 2021-09-22
[PATCH v3 11/16] KVM: x86: More precisely identify NMI from guest when handling PMI · Sean Christopherson <seanjc@google.com> · 2021-09-22
Re: [PATCH v3 11/16] KVM: x86: More precisely identify NMI from guest when handling PMI · Paolo Bonzini <pbonzini@redhat.com> · 2021-09-22
[PATCH v3 12/16] KVM: Move x86's perf guest info callbacks to generic KVM · Sean Christopherson <seanjc@google.com> · 2021-09-22
Re: [PATCH v3 12/16] KVM: Move x86's perf guest info callbacks to generic KVM · Paolo Bonzini <pbonzini@redhat.com> · 2021-09-22
Re: [PATCH v3 12/16] KVM: Move x86's perf guest info callbacks to generic KVM · Marc Zyngier <maz@kernel.org> · 2021-10-11
Re: [PATCH v3 12/16] KVM: Move x86's perf guest info callbacks to generic KVM · Sean Christopherson <seanjc@google.com> · 2021-10-11
Re: [PATCH v3 12/16] KVM: Move x86's perf guest info callbacks to generic KVM · Marc Zyngier <maz@kernel.org> · 2021-10-11
[PATCH v3 13/16] KVM: x86: Move Intel Processor Trace interrupt handler to vmx.c · Sean Christopherson <seanjc@google.com> · 2021-09-22
[PATCH v3 14/16] KVM: arm64: Convert to the generic perf callbacks · Sean Christopherson <seanjc@google.com> · 2021-09-22
Re: [PATCH v3 14/16] KVM: arm64: Convert to the generic perf callbacks · Marc Zyngier <maz@kernel.org> · 2021-10-11
[PATCH v3 15/16] KVM: arm64: Drop perf.c and fold its tiny bits of code into arm.c / pmu.c · Sean Christopherson <seanjc@google.com> · 2021-09-22
Re: [PATCH v3 15/16] KVM: arm64: Drop perf.c and fold its tiny bits of code into arm.c / pmu.c · Marc Zyngier <maz@kernel.org> · 2021-10-11
Re: [PATCH v3 15/16] KVM: arm64: Drop perf.c and fold its tiny bits of code into arm.c / pmu.c · Sean Christopherson <seanjc@google.com> · 2021-11-09
[PATCH v3 16/16] perf: Drop guest callback (un)register stubs · Sean Christopherson <seanjc@google.com> · 2021-09-22
Re: [PATCH v3 16/16] perf: Drop guest callback (un)register stubs · Paolo Bonzini <pbonzini@redhat.com> · 2021-09-22
Re: [PATCH v3 00/16] perf: KVM: Fix, optimize, and clean up callbacks · Paolo Bonzini <pbonzini@redhat.com> · 2021-09-22

Re: [PATCH v3 01/16] perf: Ensure perf_guest_cbs aren't reloaded between !NULL check and deref

From: Paolo Bonzini <pbonzini@redhat.com>
Date: 2021-11-10 11:08:09
Also in: kvm, kvmarm, linux-perf-users, linux-riscv, lkml, xen-devel

On 11/4/21 15:18, Sean Christopherson wrote:

If I'm interpeting Paolo's suggestion
correctly, he's pointing out that oustanding stores to the function pointers in
@cbs need to complete before assigning a non-NULL pointer to perf_guest_cbs,
otherwise a perf event handler may see a valid pointer with half-baked callbacks.

I think smp_store_release() with a comment would be appropriate, assuming my
above interpretation is correct.

Yes, exactly.  It should even be rcu_assign_pointer(), matching the 
synchronize_rcu() in patch 1 (and the change can be done in patch 1, too).

Paolo


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