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 E654CC25B75 for ; Mon, 3 Jun 2024 09:19:21 +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:From:References:Cc:To: Subject:MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=E98D2kFv3gmfKSZuiy9JgXPCmHbiBPUX2rYm9C8tSFU=; b=goTzRfsj5lFTjg ByteaKfBduIQPwMaUXaenQU02YdGUCEawWacXPVCEaBdqllbWeMxf4yVekSH5Ik3v919wpFephofP 9WYOT91zba+dx9cqjr0urzUIybKtKlsJ8qFQXRmBF8jimBt8N/uwSY09HqCTmRyzWRCW9p2GN1dnq kH8OemXG//Jf1ZhZOvNBK1VBxppr5F7ri2d8aOqHcuS/wmU7RdM7x7HVvWcWsM/OCKZNPGH61S6mk 54I9ntVpRpixdiJ0W5G/6W/XjpcjbW8v2r5zv7WewgM6dSfYMRQyU6QIYHOQuFQS4jcrfbMU2Z5Ei uWt69LeeTqWdKtaruztA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sE3qR-0000000GAdU-1yGu; Mon, 03 Jun 2024 09:19:11 +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 1sE3qM-0000000GAbG-2pBg for linux-arm-kernel@lists.infradead.org; Mon, 03 Jun 2024 09:19:08 +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 12A551042; Mon, 3 Jun 2024 02:19:30 -0700 (PDT) Received: from [10.162.40.16] (a077893.blr.arm.com [10.162.40.16]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6D47E3F762; Mon, 3 Jun 2024 02:19:01 -0700 (PDT) Message-ID: Date: Mon, 3 Jun 2024 14:48:58 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V17 0/9] arm64/perf: Enable branch stack sampling Content-Language: en-US To: James Clark Cc: 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, mark.rutland@arm.com References: <20240405024639.1179064-1-anshuman.khandual@arm.com> <5f8fdfd2-a4f9-4fde-ad24-3b76231e61c8@arm.com> From: Anshuman Khandual In-Reply-To: <5f8fdfd2-a4f9-4fde-ad24-3b76231e61c8@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240603_021906_811329_BB52AE0F X-CRM114-Status: GOOD ( 16.49 ) 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 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. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel