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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 85504C433EF for ; Thu, 7 Jul 2022 14:38:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235828AbiGGOiC (ORCPT ); Thu, 7 Jul 2022 10:38:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59228 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235486AbiGGOiB (ORCPT ); Thu, 7 Jul 2022 10:38:01 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 8D0C530F6F for ; Thu, 7 Jul 2022 07:38:00 -0700 (PDT) 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 7F3021063; Thu, 7 Jul 2022 07:38:00 -0700 (PDT) Received: from [192.168.122.164] (U203867.austin.arm.com [10.118.30.29]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 75EC63F66F; Thu, 7 Jul 2022 07:37:58 -0700 (PDT) Message-ID: <4b99cf3c-f40b-cba7-2fa2-b6b311859776@arm.com> Date: Thu, 7 Jul 2022 09:37:57 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: [PATCH 5/8] arm64: Create cache sysfs directory without ACPI PPTT for hardware prefetch control Content-Language: en-US To: "tarumizu.kohei@fujitsu.com" , 'Sudeep Holla' Cc: "catalin.marinas@arm.com" , "will@kernel.org" , "tglx@linutronix.de" , "mingo@redhat.com" , "bp@alien8.de" , "dave.hansen@linux.intel.com" , "x86@kernel.org" , "hpa@zytor.com" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" References: <20220125071414.811344-1-tarumizu.kohei@fujitsu.com> <20220125071414.811344-6-tarumizu.kohei@fujitsu.com> <20220126103614.pcrcuc2kzklkq3xa@bogus> From: Jeremy Linton In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 2/1/22 05:56, tarumizu.kohei@fujitsu.com wrote: >> I am assuming this is ACPI enabled system. > > Yes, it is ACPI enabled system. > >> This looks bit hacky in my opinion. Before I explore better way of adding it, I would >> like to check if you have explored ways to add PPTT reading these registers from >> UEFI/EDK2 as PPTT has other topology information which you will need anyways. >> That would simplify handling of these cacheinfo sysfs in the kernel. Let me know >> what are your thoughts ? > > The latest firmware of ARM64 machine, FX700 with the A64FX processor > does not support PPTT. > I think adding PPTT is the best way to generate cacheinfo sysfs. > However, it is difficult to modify the firmware to add PPTT, so > it is not clear when it will be possible. > Therefore, I would like to implement the function in the kernel on > the condition that firmware does not support PPTT. As a bit of a late comment here, I assume you tried injecting the PPTT via the initrd (directions in admin-guide/acpi/initrd_table_override.txt) then? That is one of the usual kernel workarounds for broken/missing ACPI tables. As mentioned above, besides not providing appropriate topology information to userspace, not having the PPTT is also possibly causing suboptimal scheduling decisions in the kernel itself.