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[84.236.113.97]) by smtp.gmail.com with ESMTPSA id n7-20020a170906840700b00a46caa13e67sm5112440ejx.105.2024.04.01.02.29.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 Apr 2024 02:29:59 -0700 (PDT) Sender: Ingo Molnar Date: Mon, 1 Apr 2024 11:29:57 +0200 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 v4 0/4] perf/x86/amd: add LBR capture support outside of hardware events Message-ID: References: <20240331041830.2806741-1-andrii@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@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: <20240331041830.2806741-1-andrii@kernel.org> * Andrii Nakryiko wrote: > Add AMD-specific implementation of perf_snapshot_branch_stack static call that > allows LBR capture from arbitrary points in the kernel. This is utilized by > BPF programs. See patch #3 for all the details. > > Patches #1 and #2 are preparatory steps to ensure LBR freezing is completely > inlined and have no branches, to minimize LBR snapshot contamination. > > Patch #4 removes an artificial restriction on perf events with LBR enabled. > > Andrii Nakryiko (4): > perf/x86/amd: ensure amd_pmu_core_disable_all() is always inlined > perf/x86/amd: avoid taking branches before disabling LBR > perf/x86/amd: support capturing LBR from software events > perf/x86/amd: don't reject non-sampling events with configured LBR > > arch/x86/events/amd/core.c | 37 +++++++++++++++++++++++++++++++++++- > arch/x86/events/amd/lbr.c | 11 +---------- > arch/x86/events/perf_event.h | 11 +++++++++++ > 3 files changed, 48 insertions(+), 11 deletions(-) So there's a new conflict with patch #2, probably due to interaction with this recent fix that is now upstream: 598c2fafc06f ("perf/x86/amd/lbr: Use freeze based on availability") I don't think it should change the logic of the snapshot feature materially, X86_FEATURE_AMD_LBR_PMC_FREEZE should be orthogonal to it, as the LBR snapshot isn't taken from a PMI. Thanks, Ingo