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 9B8BAC43334 for ; Thu, 7 Jul 2022 14:46:33 +0000 (UTC) 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=yp6cQlDSjyCuGo7nrgbnqvTpN8agS5cDWFbAcXRWJgo=; b=wL2SypkVB9pAa5 jkinm+eMwQNTgPokVYmpSttk4hfvBHviSnVPvV6kNRKd5o2VaVO5q/K7GvoSIWTV8x/Z/j5qHmGui zOMWiuwToyL0kc/WrHEEInchc/attouUhrs7aSyQJbO2Npv1Pw6VmIsAxnK0Dirxc5T+kHIL0FuqZ ygbrMsOWnRTz/BjXgVRtS7zPvgW3Mq8/J+QQwlup6cIBSqEZM3Kfx4KM2eOQJRy2ODimohPV6L1TY VDF3hVYYfwByzPg07q3Jv6M7KvVMcF7oUvquO06jejHH2I3GxWl0c6t+pJDaFLI3Csk9SKDSFfQK6 0e/5Xz9/LHhjr4hHHM3A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1o9Skt-00GZX5-5f; Thu, 07 Jul 2022 14:45:23 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1o9Skp-00GZVO-Gf for linux-arm-kernel@lists.infradead.org; Thu, 07 Jul 2022 14:45:21 +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 5BC03106F; Thu, 7 Jul 2022 07:45:18 -0700 (PDT) Received: from bogus (unknown [10.57.39.193]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A8A383F66F; Thu, 7 Jul 2022 07:45:15 -0700 (PDT) Date: Thu, 7 Jul 2022 15:44:04 +0100 From: Sudeep Holla To: Jeremy Linton Cc: "tarumizu.kohei@fujitsu.com" , "catalin.marinas@arm.com" , Sudeep Holla , "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" Subject: Re: [PATCH 5/8] arm64: Create cache sysfs directory without ACPI PPTT for hardware prefetch control Message-ID: <20220707144404.pm3qtgfo6fsik77d@bogus> References: <20220125071414.811344-1-tarumizu.kohei@fujitsu.com> <20220125071414.811344-6-tarumizu.kohei@fujitsu.com> <20220126103614.pcrcuc2kzklkq3xa@bogus> <4b99cf3c-f40b-cba7-2fa2-b6b311859776@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <4b99cf3c-f40b-cba7-2fa2-b6b311859776@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220707_074519_638148_A16A3555 X-CRM114-Status: GOOD ( 26.83 ) 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 Thu, Jul 07, 2022 at 09:37:57AM -0500, Jeremy Linton wrote: > 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. > Thanks a lot for the suggestion Jeremy. For some reason, I missed to follow up on this after my initial response. Anyways I agree injecting PPTT via initrd is a good compromise on systems that are shipped without or broken PPTT. I have tested that to be fully functional on v5.19-rc* on one of the servers shipped with broken PPTT. -- Regards, Sudeep _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel