From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E8EA740E8DB; Fri, 5 Jun 2026 13:53:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780667633; cv=none; b=L9g1ozr+F6GHSLT0EACBvm600eiq9EZgVgJwgKFbfA9i1VDcTmTYb+zCUDNSgnB73VqWfndWHML69tQ+Z+LEOpTHHUBDmZwd/yQJUlXWeIMMoUjAdSh3Ib+NAbJ6Ol+SZ112H0fsxxtd19LVpRaKcBCDhpF7KaaFAK0Bbwemj7c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780667633; c=relaxed/simple; bh=dv7w7V243Ir0z2lVM+UUtdm7LPvO4BCpPqes1rH4Faw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=CbeK39PLi7m4sk7F0mY8ANUTQrhtLEfKsICZRSIvXB59UbJR2tNItKydpnAFYfwuCzHzBltIiyQg7rmS1CtrtKuYhTRVKS5FPhd2iBcIeuY6AkpoVzS1+yJIYfmyhnYXAySWPyQpvcgxd4gGdi9aEK3fr2Q219LmjBE5VaC7zEg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=A9St+RvV; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="A9St+RvV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 82EE71F00898; Fri, 5 Jun 2026 13:53:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780667632; bh=J0R4eBG2pFYNvoAv6aArk0OSJ05uyndW9ZEtAs++bJk=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=A9St+RvVrzyZl1ZMltNKutIQ4v56AK9zs+Vr6o/Gw9W8YZzAgleY83Gj5tnrWqydv AdT056a/FPR/9138v3+ImH4wqZtMbBAYNqbYRQPuIe9Tt4Q8tsPXSyqMYCwyrd4RMv A77jBow2Hfw7i08PjR8ogFZQ9YU3f7fvI7U+y+5KYtTh6fESF/Ezz9WCfT+21oizXA 5vS0IiejhSADD+AjeTi1nsCORC1GBX2JrZy+nrPEcfktzLtTj85ZM7HuO9kxmfAgeO abA/pREttTxluz8Ydipn9WHLOzoipIwUI1hZwuS7laf3zAoMttwO/y/Z0OatWqDVf9 sc9zAKaZVrkOQ== Date: Fri, 5 Jun 2026 08:53:51 -0500 From: Rob Herring To: Puranjay Mohan Cc: bpf@vger.kernel.org, Puranjay Mohan , Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , Will Deacon , Mark Rutland , Catalin Marinas , Leo Yan , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , James Clark , Ian Rogers , Adrian Hunter , Shuah Khan , Breno Leitao , Ravi Bangoria , Stephane Eranian , Kumar Kartikeya Dwivedi , Usama Arif , linux-arm-kernel@lists.infradead.org, linux-perf-users@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH v4 3/4] perf/arm64: Add BRBE support for bpf_get_branch_snapshot() Message-ID: <20260605135351.GA3587043-robh@kernel.org> References: <20260527121207.2312181-1-puranjay@kernel.org> <20260527121207.2312181-4-puranjay@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: <20260527121207.2312181-4-puranjay@kernel.org> On Wed, May 27, 2026 at 05:11:59AM -0700, Puranjay Mohan wrote: > Enable bpf_get_branch_snapshot() on ARM64 by implementing the > perf_snapshot_branch_stack static call for BRBE. > > BRBE is paused before masking exceptions to avoid branch buffer > pollution from trace_hardirqs_off(). Exceptions are then masked with > local_daif_save() to prevent PMU overflow pseudo-NMIs from interfering. > If an overflow between pause and DAIF save re-enables BRBE, the snapshot > detects this via BRBFCR_EL1.PAUSED and bails out. > > Branch records are read using perf_entry_from_brbe_regset() with a NULL > event pointer to bypass event-specific filtering. The buffer is > invalidated after reading. > > Introduce a for_each_brbe_entry() iterator to deduplicate bank > iteration between brbe_read_filtered_entries() and the snapshot. > > Signed-off-by: Puranjay Mohan > --- > drivers/perf/arm_brbe.c | 127 ++++++++++++++++++++++++++++++++------- > drivers/perf/arm_brbe.h | 9 +++ > drivers/perf/arm_pmuv3.c | 5 +- > 3 files changed, 119 insertions(+), 22 deletions(-) Reviewed-by: Rob Herring (Arm)