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 663C6C021A0 for ; Thu, 13 Feb 2025 12:29:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=u1gp+v/xUd838KTXnOpW+gE7GMlB17UGSSaBKAG+Jgc=; b=KpYBjHTur8zmPmAiNno90yE1Fv HYK2uLP2G61HgfJE6wBHE+cxgu0T3erGwvyqX621QJrzaCKSYpEcr9WW0s8Meq36PiXaRTkc+Z/iq IKp1pIy8i01MwLXKskrkGcooTN7W+4+Yp+/j2IDpRjF5Ut6Un55Pb6y8J1bf74yu9on6iZlNjivVg lShrMhQ6EZquFunmWjIDmhdSUJw5ACRutVg1w5sJZtCzL38XJxW57mU0uDkTjuml/v8622mcepksP 2w/d5bHs7YiRkIXy1wmCooDETEhQANHDMW82IhuKWbaqf8rZSvBLmJXclOq5M7W/yYN8Q1IN1ZBkx 4uqVS8yQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tiYLX-0000000B0kV-3B0H; Thu, 13 Feb 2025 12:29:35 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tiYJT-0000000B0DB-2g2C for linux-arm-kernel@lists.infradead.org; Thu, 13 Feb 2025 12:27:29 +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 A29571756; Thu, 13 Feb 2025 04:27:45 -0800 (PST) Received: from localhost (e132581.arm.com [10.2.76.71]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8C05E3F6A8; Thu, 13 Feb 2025 04:27:24 -0800 (PST) Date: Thu, 13 Feb 2025 12:27:19 +0000 From: Leo Yan To: Rob Herring Cc: Will Deacon , Mark Rutland , Catalin Marinas , Jonathan Corbet , Marc Zyngier , Oliver Upton , Joey Gouly , Suzuki K Poulose , Zenghui Yu , James Clark , Anshuman Khandual , linux-arm-kernel@lists.infradead.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kvmarm@lists.linux.dev Subject: Re: [PATCH v19 09/11] arm64: Handle BRBE booting requirements Message-ID: <20250213122719.GE235556@e132581.arm.com> References: <20250202-arm-brbe-v19-v19-0-1c1300802385@kernel.org> <20250202-arm-brbe-v19-v19-9-1c1300802385@kernel.org> <20250212121046.GB235556@e132581.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250213_042727_718015_B258EE21 X-CRM114-Status: GOOD ( 13.27 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Feb 12, 2025 at 03:21:46PM -0600, Rob Herring wrote: [...] > > > + - If the kernel is entered at EL1 and EL2 is present: > > > + > > > + - BRBCR_EL2.CC (bit 3) must be initialised to 0b1. > > > + - BRBCR_EL2.MPRED (bit 4) must be initialised to 0b1. > > > > Should clarify BRBCR_EL2.TS to be initialised to 0b00 ? Arm ARM > > claims the reset behaviour of the TS field is unknown value. The > > assembly code below actually has initializes the TS field as zero. > > Humm, we don't currently care what it is initialized to because the > timestamp is never used. We would care in the future if we use > timestamps. Will 0b00 be the only correct value? I'm not sure. In initializaton phase, if set BRBCR_EL2.TS = 0b00, then the timestamp will be decided by BRBCR_EL1.TS. I expect the BRBE driver will always write BRBCR_EL1.TS. Thanks, Leo