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 X-Spam-Level: X-Spam-Status: No, score=-4.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6D51EC433DB for ; Tue, 12 Jan 2021 14:46:59 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 05C4823121 for ; Tue, 12 Jan 2021 14:46:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 05C4823121 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:Message-ID:References:In-Reply-To:Subject:To:From: Date:MIME-Version:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Jvo4v6C6uacRQHKhBmW9JGU9goPtxN44/iKk1YpOyJ0=; b=0kuVHYxsxy2/v9sK803pobWX5 EF1VL5J0UGCwIZVwq8vyO1h7+Svml0itxZXswUeyWc7ojrWQW3df2+JjPc8GrLLOQ53VgHNsOjnqz yBpULPyniuGC/ifH69/8hUQQaTV7Pk7f7uBnremNlNRytAc/ZmXbEYr57iyfSYyiGMXm8X+2F2ZYK WeLaIBRwqMbXRR985c4DqG7NPQY0cPVstHgyKzwoq9HNLSMRLnN5fGe2G9jZHZNzWeehFEX4n1K9P h5tWpvSxpSN2LfDLDm1cbtFGS/6mzgnc3Y0BLqtX457g1e9sOb5Gn8mw//DJpuRzmZ4ddIldbg5tH U7bTXj7XQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kzKvI-0006hl-9T; Tue, 12 Jan 2021 14:45:28 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kzKvE-0006g9-4n for linux-arm-kernel@lists.infradead.org; Tue, 12 Jan 2021 14:45:26 +0000 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7E59223121; Tue, 12 Jan 2021 14:45:22 +0000 (UTC) Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94) (envelope-from ) id 1kzKvA-006ztI-Fo; Tue, 12 Jan 2021 14:45:20 +0000 MIME-Version: 1.0 Date: Tue, 12 Jan 2021 14:45:20 +0000 From: Marc Zyngier To: Chanho Park Subject: Re: [PATCH] clocksource/drivers/arm_arch_timer: export arch_timer_get_rate In-Reply-To: References: <20210112013140.35979-1-chanho61.park@samsung.com> <20210112101247.GA34326@C02TD0UTHF1T.local> User-Agent: Roundcube Webmail/1.4.9 Message-ID: <7123dff576287de381c93abb88d9e283@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: parkch98@gmail.com, mark.rutland@arm.com, linux-arm-kernel@lists.infradead.org, chanho61.park@samsung.com, daniel.lezcano@linaro.org, tglx@linutronix.de X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210112_094524_297275_F7F193E6 X-CRM114-Status: GOOD ( 20.16 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Chanho Park , Daniel Lezcano , Thomas Gleixner , linux-arm-kernel@lists.infradead.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2021-01-12 13:39, Chanho Park wrote: > Hi, > >> On Tue, Jan 12, 2021 at 10:31:40AM +0900, Chanho Park wrote: >> > This patch adds to export arch_timer_get_rate function for calculating >> > absolute timestamp which is based on arch timer like below. >> > arch_timer_read_counter was already exported but arch_timer_get_rate >> > wasn't. Thus, this patch tries to export this to use this function from >> > loadable kernel module. >> >> Can you please explain /where/ this would be used? i.e. which module? >> >> Generally we try to avoid drivers depending on the specific >> clocksource, >> so I think there needs to be stronger rationale for exposing this. > > I need a system-wide timestamp which can be available from bootloader > and kernel stages including virtual machines. > Actually, it's necessary to record a timestamp of each log message for > system-wide debugging on type-1 hypervisor. > RTC can be used for this purpose but we should make it to hypervisor > awareness. > |---------------|-------------------------| > Bootloader VM1 (Guest) > |-------------------------| > VM2 (Guest) > > So, the easiest way is using the arm architect timer's timestamp > because it's already supported on each VM by the hypervisor. This doesn't make much sense. The hypervisor and the VMs are independent software entities, and they don't use symbols from each other. So this symbol is probably used by a module *inside* the VMs, and Mark's question still stands. Thanks, M. -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel