From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id E0C6C1DCB2D; Mon, 28 Oct 2024 13:43:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730123024; cv=none; b=KyrjQlIXphI+pYYlv21K6RTO1G8Va345VMg5VSntDudjpQLwntEmxvaT+Wwm58UtDLrTkPzAbOB0F+zxBXVOHHI98yEELHtOsb9pYBfoxrnbzyEIta0W7qZGjsBiqxeWLAqZAunS0s0ClRBiPqmZPobu5/c0O7pSzaR8WjiKpLk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730123024; c=relaxed/simple; bh=uMi/PJfX0ne0yB7ZpkaQrwY7lz0yJr3IHebiWoYUnbM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=XHPqLllFfiBZxOb5HjKCdOKy9qTCD1cVcmGwwoRQvQ1IK3XRN2nRvZ6p7+YhImFvsH9QWdY3Sd0pa8VQ+T053nHbgsA2XVDw9yogzqBOcddiq/9MY+o6IQqB4ADv0WeS7OXv8RAghpXWwbrEy1IjGMVdsnlQdukp9AP5tmPXUgk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 02037497; Mon, 28 Oct 2024 06:44:11 -0700 (PDT) Received: from [10.163.42.200] (unknown [10.163.42.200]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3C4103F66E; Mon, 28 Oct 2024 06:43:36 -0700 (PDT) Message-ID: <92124be9-ffa5-4cf9-bec4-e7d3afb91a96@arm.com> Date: Mon, 28 Oct 2024 19:13:33 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/3] arm64/boot: Enable EL2 requirements for FEAT_Debugv8p9 To: Mark Rutland Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Jonathan Corbet , Marc Zyngier , Oliver Upton , James Morse , Suzuki K Poulose , Catalin Marinas , Will Deacon , Mark Brown , kvmarm@lists.linux.dev, linux-doc@vger.kernel.org References: <20241001043602.1116991-1-anshuman.khandual@arm.com> <20241001043602.1116991-3-anshuman.khandual@arm.com> <72700154-cbf4-4a0a-b6e2-6f0709dec0ce@arm.com> Content-Language: en-US From: Anshuman Khandual In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/28/24 18:05, Mark Rutland wrote: > On Wed, Oct 23, 2024 at 11:42:37AM +0530, Anshuman Khandual wrote: >> >> >> On 10/22/24 21:40, Mark Rutland wrote: >>> On Tue, Oct 01, 2024 at 10:06:01AM +0530, Anshuman Khandual wrote: >>>> Fine grained trap control for MDSELR_EL1 register needs to be configured in >>>> HDFGRTR2_EL2, and HDFGWTR2_EL2 registers when kernel enters at EL1, but EL2 >>>> is also present. This adds a new helper __init_el2_fgt2() initializing this >>>> new FEAT_FGT2 based fine grained registers. >>>> >>>> MDCR_EL2.EBWE needs to be enabled for additional (beyond 16) breakpoint and >>>> watchpoint exceptions when kernel enters at EL1, but EL2 is also present. >>>> This updates __init_el2_debug() as required for FEAT_Debugv8p9. >>>> >>>> While here, also update booting.rst with MDCR_EL3 and SCR_EL3 requirements. >>> >>> [...] >>> >>>> + For CPUs with FEAT_Debugv8p9 extension present: >>>> + >>>> + - If the kernel is entered at EL1 and EL2 is present: >>>> + >>>> + - HDFGRTR2_EL2.nMDSELR_EL1 (bit 5) must be initialized to 0b1 >>>> + - HDFGWTR2_EL2.nMDSELR_EL1 (bit 5) must be initialized to 0b1 >>>> + - MDCR_EL2.EBWE (bit 43) must be initialized to 0b1 >>>> + >>>> + - If EL3 is present: >>>> + >>>> + - MDCR_EL3.TDA (bit 9) must be initialized to 0b0 >>> >>> AFAICT we need TDA==0 this regardless of FEAT_Debugv8p9 (and e.g. we need >> >> That's because MDCR_EL3.TDA=0, enables access to many other debug registers >> beside FEAT_Debugv8p9, which are currently used and hence this MDCR_EL3.TDA >> =0 requirement is a not a new one but rather a missing one instead ? > > Yes, that's why I said we need it regardless; it's an existing > requirement that wasn't documented. Alright, got it. > >> >>> MDCR_EL3.TPM==0 where FEAT_PMUv3 is implemented), so we should probably >>> check if there's anything else we haven't yet documented in MDCR_EL3. >> >> Will scan through MDCR_EL3 register and match it with existing documentation >> i.e Documentation/arch/arm64/booting.rst. If there are some missing MDCR_EL3 >> fields which should be mentioned, will add them via a separate pre-requisite >> patch ? > > Yes please. > > Mark. Sure, will separate those changes in a pre-requisite patch as suggested.