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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id o1sm1112414wru.91.2021.09.21.23.23.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 Sep 2021 23:23:34 -0700 (PDT) Subject: Re: [PATCH v3 02/16] KVM: x86: Register perf callbacks after calling vendor's hardware_setup() To: Sean Christopherson , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Will Deacon , Mark Rutland , Marc Zyngier , Guo Ren , Nick Hu , Greentime Hu , Vincent Chen , Paul Walmsley , Palmer Dabbelt , Albert Ou , Boris Ostrovsky , Juergen Gross Cc: Alexander Shishkin , Jiri Olsa , Namhyung Kim , James Morse , Alexandru Elisei , Suzuki K Poulose , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Stefano Stabellini , linux-arm-kernel@lists.infradead.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, kvmarm@lists.cs.columbia.edu, linux-csky@vger.kernel.org, linux-riscv@lists.infradead.org, kvm@vger.kernel.org, xen-devel@lists.xenproject.org, Artem Kashkanov , Like Xu , Zhu Lingshan References: <20210922000533.713300-1-seanjc@google.com> <20210922000533.713300-3-seanjc@google.com> From: Paolo Bonzini Message-ID: <6e31f767-ae3d-ec87-9880-5a8ebc381192@redhat.com> Date: Wed, 22 Sep 2021 08:23:25 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210922000533.713300-3-seanjc@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22/09/21 02:05, Sean Christopherson wrote: > Wait to register perf callbacks until after doing vendor hardaware setup. > VMX's hardware_setup() configures Intel Processor Trace (PT) mode, and a > future fix to register the Intel PT guest interrupt hook if and only if > Intel PT is exposed to the guest will consume the configured PT mode. > > Delaying registration to hardware setup is effectively a nop as KVM's perf > hooks all pivot on the per-CPU current_vcpu, which is non-NULL only when > KVM is handling an IRQ/NMI in a VM-Exit path. I.e. current_vcpu will be > NULL throughout both kvm_arch_init() and kvm_arch_hardware_setup(). > > Cc: Alexander Shishkin > Cc: Artem Kashkanov > Cc: stable@vger.kernel.org > Signed-off-by: Sean Christopherson > --- > arch/x86/kvm/x86.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 86539c1686fa..fb6015f97f9e 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -8426,8 +8426,6 @@ int kvm_arch_init(void *opaque) > > kvm_timer_init(); > > - perf_register_guest_info_callbacks(&kvm_guest_cbs); > - > if (boot_cpu_has(X86_FEATURE_XSAVE)) { > host_xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK); > supported_xcr0 = host_xcr0 & KVM_SUPPORTED_XCR0; > @@ -8461,7 +8459,6 @@ void kvm_arch_exit(void) > clear_hv_tscchange_cb(); > #endif > kvm_lapic_exit(); > - perf_unregister_guest_info_callbacks(&kvm_guest_cbs); > > if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) > cpufreq_unregister_notifier(&kvmclock_cpufreq_notifier_block, > @@ -11064,6 +11061,8 @@ int kvm_arch_hardware_setup(void *opaque) > memcpy(&kvm_x86_ops, ops->runtime_ops, sizeof(kvm_x86_ops)); > kvm_ops_static_call_update(); > > + perf_register_guest_info_callbacks(&kvm_guest_cbs); > + > if (!kvm_cpu_cap_has(X86_FEATURE_XSAVES)) > supported_xss = 0; > > @@ -11091,6 +11090,8 @@ int kvm_arch_hardware_setup(void *opaque) > > void kvm_arch_hardware_unsetup(void) > { > + perf_unregister_guest_info_callbacks(&kvm_guest_cbs); > + > static_call(kvm_x86_hardware_unsetup)(); > } > > Acked-by: Paolo Bonzini