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[195.38.112.2]) by smtp.gmail.com with ESMTPSA id lh23-20020a170906f8d700b00a46ab5aaffcsm1636675ejb.178.2024.03.29.00.43.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 29 Mar 2024 00:43:15 -0700 (PDT) Sender: Ingo Molnar Date: Fri, 29 Mar 2024 08:43:13 +0100 From: Ingo Molnar To: Andrii Nakryiko Cc: x86@kernel.org, peterz@infradead.org, mingo@redhat.com, tglx@linutronix.de, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, jolsa@kernel.org, song@kernel.org, kernel-team@meta.com Subject: Re: [PATCH v2] perf/x86/amd: support capturing LBR from software events Message-ID: References: <20240328133359.731818-1-andrii@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240328133359.731818-1-andrii@kernel.org> * Andrii Nakryiko wrote: > Now that it's possible to capture LBR on AMD CPU from BPF at arbitrary > point, there is no reason to artificially limit this feature to sampling > events. So corresponding check is removed. AFAIU, there is no > correctness implications of doing this (and it was possible to bypass > this check by just setting perf_event's sample_period to 1 anyways, so > it doesn't guard all that much). > diff --git a/arch/x86/events/amd/lbr.c b/arch/x86/events/amd/lbr.c > index 4a1e600314d5..75920f895d67 100644 > --- a/arch/x86/events/amd/lbr.c > +++ b/arch/x86/events/amd/lbr.c > @@ -310,10 +310,6 @@ int amd_pmu_lbr_hw_config(struct perf_event *event) > { > int ret = 0; > > - /* LBR is not recommended in counting mode */ > - if (!is_sampling_event(event)) > - return -EINVAL; > - Could you please split out this change into a separate patch? Thanks, Ingo