From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A7C54C25B75 for ; Mon, 3 Jun 2024 09:39:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=QHjhVokcU9TtJTqBk4LsyVCtyFcF7b83BX6ktGiOshw=; b=lcyllz0Dmo6F/0 P9651nmW/mTHQ14NyTFTobhir+G4kg/R/nrKdtFK5nwhmCh/IPuON2ZlQ6PwmS/VHcEYBJQUvmsYf i0BAeno3ti2DjScU7mZTxTlYzhszTZ77oISlttgXt4N2xJ9kDVoxhY7v6xNolBFOKcrB0uT1QOvNb RDfegoZ0MaghomYi6MYUM5WFEqNod6QQ3Q2H33FUreo6rTtJQKostqbNX5q1PPh0UOhM3k5+tHbkT GZYFjN7EKUCbKVbeE2nDu1Zaemun4MWjCrtEvTpbVyBPKgYNhqKntWVEb7XcG0pSgsFSekx1E86BX mO5ezZwAGKCeqEfMWmGg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sE4AE-0000000GGs3-38tA; Mon, 03 Jun 2024 09:39:38 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sE4AB-0000000GGpP-0HrE for linux-arm-kernel@lists.infradead.org; Mon, 03 Jun 2024 09:39:36 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D7C0D1042; Mon, 3 Jun 2024 02:39:58 -0700 (PDT) Received: from J2N7QTR9R3 (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6CD153F762; Mon, 3 Jun 2024 02:39:32 -0700 (PDT) Date: Mon, 3 Jun 2024 10:39:30 +0100 From: Mark Rutland To: Anshuman Khandual Cc: James Clark , Mark Brown , Rob Herring , Marc Zyngier , Suzuki Poulose , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , linux-perf-users@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, will@kernel.org, catalin.marinas@arm.com Subject: Re: [PATCH V17 0/9] arm64/perf: Enable branch stack sampling Message-ID: References: <20240405024639.1179064-1-anshuman.khandual@arm.com> <5f8fdfd2-a4f9-4fde-ad24-3b76231e61c8@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240603_023935_258275_139EE93F X-CRM114-Status: GOOD ( 23.87 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Jun 03, 2024 at 02:48:58PM +0530, Anshuman Khandual wrote: > > > On 5/30/24 15:33, James Clark wrote: > > > > > > On 05/04/2024 03:46, Anshuman Khandual wrote: > >> This series enables perf branch stack sampling support on arm64 platform > >> via a new arch feature called Branch Record Buffer Extension (BRBE). All > >> the relevant register definitions could be accessed here. > >> > >> https://developer.arm.com/documentation/ddi0601/2021-12/AArch64-Registers > >> > >> This series applies on 6.9-rc2. > >> > >> Also this series is being hosted below for quick access, review and test. > >> > >> https://git.gitlab.arm.com/linux-arm/linux-anshuman.git (brbe_v17) > >> > >> There are still some open questions regarding handling multiple perf events > >> with different privilege branch filters getting on the same PMU, supporting > >> guest branch stack tracing from the host etc. Finally also looking for some > >> suggestions regarding supporting BRBE inside the guest. The series has been > >> re-organized completely as suggested earlier. > > > > For guest support I'm still of this opinion: > > > > * No support for the host looking into guests (the addresses don't > > make sense anyway without also running Perf record in the guest) > > * Save and restore the host buffer and registers on guest switch (if > > it was ever used by either host or guest) > > * Let the guest do whatever it wants with BRBE without any > > virtualisation > > > > Merging this with the current PMU virtualistion stuff seems like a lot > > of work for no use case (host looking into guests). Having said that, it > > might not even be worth discussing on this patchset apart from "no guest > > support", and we can do it later to avoid confusion that it's being > > proposed for this version. > > Agreed, let's just have "no guest support" for now in this proposed series > without any more additional changes to keep things simpler and separated. > I will also update the cover letter next time around making this clear. FWIW, that sounds good to me. Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel