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[149.6.153.186]) by smtp.googlemail.com with ESMTPSA id j16-20020a05600c191000b0038ca3500494sm16631476wmq.27.2022.04.08.09.24.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 08 Apr 2022 09:24:06 -0700 (PDT) Message-ID: <3c11308e-006a-a7e9-8482-c6b341690530@redhat.com> Date: Fri, 8 Apr 2022 18:24:05 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 To: Mathieu Desnoyers , Sean Christopherson References: <1218866473.10909.1649432186473.JavaMail.zimbra@efficios.com> In-Reply-To: <1218866473.10909.1649432186473.JavaMail.zimbra@efficios.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Subject: Re: [lttng-dev] Unexport of kvm_x86_ops vs tracer modules X-BeenThere: lttng-dev@lists.lttng.org X-Mailman-Version: 2.1.39 Precedence: list List-Id: LTTng development list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Paolo Bonzini via lttng-dev Reply-To: Paolo Bonzini Cc: lttng-dev , rostedt , kvm@vger.kernel.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: lttng-dev-bounces@lists.lttng.org Sender: "lttng-dev" On 4/8/22 17:36, Mathieu Desnoyers wrote: > LTTng is an out of tree kernel module, which currently relies on the export. > Indeed, arch/x86/kvm/x86.c exports a set of tracepoints to kernel modules, e.g.: > > EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_entry) > > But any probe implementation hooking on that tracepoint would need kvm_x86_ops > to translate the struct kvm_vcpu * into meaningful tracing data. > > I could work-around this on my side in ugly ways, but I would like to discuss > how kernel module tracers are expected to implement kvm events probes without > the kvm_x86_ops symbol ? The conversion is done in the TP_fast_assign snippets, which are part of kvm.ko and therefore do not need the export. As I understand it, the issue is that LTTng cannot use the TP_fast_assign snippets, because they are embedded in the trace_event_raw_event_* symbols? We cannot do the extraction before calling trace_kvm_exit, because it's expensive. Paolo _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev