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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 328C6C433EF for ; Fri, 19 Nov 2021 11:27:50 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id D5EC761AFB for ; Fri, 19 Nov 2021 11:27:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org D5EC761AFB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org 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=li6DUWa59u5cUmtfzroRIomDnxWg1lwoP4KAaCsyoI4=; b=xjeyVacnidTAbR G8bz8iTSHiFmPhcAbL65l3tvDXazhWnEdnRTgDAM1yqmTuZvDy7AVy/EM/aeyk1usMF2LD91BCWOQ hD/HdnoVjbFO/r/WaqtshBlKx/aw2ZbIPE7oo7EsKFJJ06sFPQfrtK1LJNS8cmjOsGJg19nOsXCo3 7tebhBALI4ZE2ZctMbcSjNvvU59gaaq+5WdW9Ne9wVyMx6V3iR82owe4VAIsaT+U1LnFGcIewYCW0 HxXgzPGa/IE5N9j5+1huB0bePg59XNvdEul9lVEcme+LgEureVlyldsj5vYkf2Caeg7ULuPa2yhTQ Ki8PabwmIpCujK2k/ebw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mo22O-00AFTk-N7; Fri, 19 Nov 2021 11:26:36 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mo22L-00AFSp-5M for linux-arm-kernel@lists.infradead.org; Fri, 19 Nov 2021 11:26:34 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1637321191; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Ur6jyg8LpW6xWlgk/Y4mQFrqjPeSvFG+Pwu0kvvPhXs=; b=cQX69geF942w39J0ODxIdSfyN0SzXVp2L5p5rNInMzjrGNOLqkvFARWrGAwqL6LfBb3Zf0 q2cdYt500RfRIiAYjykME5jA6Pc4zuiPruB6+CB/Z45kgW9dVXLvcwmm5vfXMpfzJsXaA8 fDq7k/8pDw7jJoA6UomTQ3cQzv9ntk0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-208-CDXegAY1OE6UozhJaY8iTA-1; Fri, 19 Nov 2021 06:26:30 -0500 X-MC-Unique: CDXegAY1OE6UozhJaY8iTA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 86E8410247A6; Fri, 19 Nov 2021 11:26:28 +0000 (UTC) Received: from fuller.cnet (ovpn-112-3.gru2.redhat.com [10.97.112.3]) by smtp.corp.redhat.com (Postfix) with ESMTPS id F37DF5C3E0; Fri, 19 Nov 2021 11:26:27 +0000 (UTC) Received: by fuller.cnet (Postfix, from userid 1000) id 65F894172ED4; Fri, 19 Nov 2021 08:26:24 -0300 (-03) Date: Fri, 19 Nov 2021 08:26:24 -0300 From: Marcelo Tosatti To: Nicolas Saenz Julienne Cc: linux-arm-kernel@lists.infradead.org, maz@kernel.org, rostedt@goodmis.org, james.morse@arm.com, alexandru.elisei@arm.com, suzuki.poulose@arm.com, catalin.marinas@arm.com, will@kernel.org, linux-kernel@vger.kernel.org, kvmarm@lists.cs.columbia.edu, mingo@redhat.com, nilal@redhat.com Subject: Re: [RFC PATCH 1/2] arm64/tracing: add cntvct based trace clock Message-ID: <20211119112624.GA51423@fuller.cnet> References: <20211119102117.22304-1-nsaenzju@redhat.com> <20211119102117.22304-2-nsaenzju@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20211119102117.22304-2-nsaenzju@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211119_032633_405236_39083259 X-CRM114-Status: GOOD ( 15.58 ) 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 Fri, Nov 19, 2021 at 11:21:17AM +0100, Nicolas Saenz Julienne wrote: > Add a new arm64-specific trace clock using the cntvct register, similar > to x64-tsc. This gives us: > - A clock that is relatively fast (1GHz on armv8.6, 1-50MHz otherwise), > monotonic, and resilient to low power modes. > - It can be used to correlate events across cpus as well as across > hypervisor and guests. > > By using arch_timer_read_counter() we make sure that armv8.6 cpus use > the less expensive CNTVCTSS_EL0, which cannot be accessed speculatively. Can this register be read by userspace ? (otherwise it won't be possible to correlate userspace events). _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel