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 X-Spam-Level: X-Spam-Status: No, score=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 617BCC47094 for ; Thu, 10 Jun 2021 13:00:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4D9AA613F1 for ; Thu, 10 Jun 2021 13:00:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229941AbhFJNCP (ORCPT ); Thu, 10 Jun 2021 09:02:15 -0400 Received: from foss.arm.com ([217.140.110.172]:59454 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230312AbhFJNCF (ORCPT ); Thu, 10 Jun 2021 09:02:05 -0400 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 86B22106F; Thu, 10 Jun 2021 06:00:08 -0700 (PDT) Received: from e113632-lin (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C09813F73D; Thu, 10 Jun 2021 06:00:05 -0700 (PDT) From: Valentin Schneider To: Will Deacon , linux-arm-kernel@lists.infradead.org Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Will Deacon , Catalin Marinas , Marc Zyngier , Greg Kroah-Hartman , Peter Zijlstra , Morten Rasmussen , Qais Yousef , Suren Baghdasaryan , Quentin Perret , Tejun Heo , Johannes Weiner , Ingo Molnar , Juri Lelli , Vincent Guittot , "Rafael J. Wysocki" , Dietmar Eggemann , Daniel Bristot de Oliveira , Mark Rutland , kernel-team@android.com Subject: Re: [PATCH v9 12/20] sched: Allow task CPU affinity to be restricted on asymmetric systems In-Reply-To: <20210608180313.11502-13-will@kernel.org> References: <20210608180313.11502-1-will@kernel.org> <20210608180313.11502-13-will@kernel.org> Date: Thu, 10 Jun 2021 14:00:03 +0100 Message-ID: <875yyldgdo.mognet@arm.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/06/21 19:03, Will Deacon wrote: > Asymmetric systems may not offer the same level of userspace ISA support > across all CPUs, meaning that some applications cannot be executed by > some CPUs. As a concrete example, upcoming arm64 big.LITTLE designs do > not feature support for 32-bit applications on both clusters. > > Although userspace can carefully manage the affinity masks for such > tasks, one place where it is particularly problematic is execve() > because the CPU on which the execve() is occurring may be incompatible > with the new application image. In such a situation, it is desirable to > restrict the affinity mask of the task and ensure that the new image is > entered on a compatible CPU. From userspace's point of view, this looks > the same as if the incompatible CPUs have been hotplugged off in the > task's affinity mask. Similarly, if a subsequent execve() reverts to > a compatible image, then the old affinity is restored if it is still > valid. > > In preparation for restricting the affinity mask for compat tasks on > arm64 systems without uniform support for 32-bit applications, introduce > {force,relax}_compatible_cpus_allowed_ptr(), which respectively restrict > and restore the affinity mask for a task based on the compatible CPUs. > > Reviewed-by: Quentin Perret > Signed-off-by: Will Deacon Reviewed-by: Valentin Schneider 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 X-Spam-Level: X-Spam-Status: No, score=-8.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BC1C5C47094 for ; Thu, 10 Jun 2021 13:02:00 +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 7E5BA61362 for ; Thu, 10 Jun 2021 13:02:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7E5BA61362 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@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:MIME-Version:Message-ID:Date:References :In-Reply-To:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=3ZtCTFCi2wktTwG8YoiWpe8PuMRn3/QsLzK6V2DVEvw=; b=5GQOJ3q2axTmZU LkSeb+Mcf2sJhl210wEbWbj7oEXmWa8WVzXfuT3wU+ERZE47xXKscN8DT8e/dek9xXX9KwLDmrMVm jdoW55NoMvoPsHUbpQJ5lRkFAFxwYn3Y5vt06zxSJmaRAeQ3AF1yJq1n8uJFibaZalYoYsTrmY2g7 2bOeMB0+TJ8dSNwp18qaVXr8LzfTMfxxNyt+gYvWgRnQWKtV22N0rshh+5cPXB7Uu2rZQOQkOZcr9 jYfa746nJqInfD2KZIhuxi4MzYLSJZfwSYMwkrrFYZHJRlt8PuH5hpiYAZ7DmuTM0xm1o0Ytbx14H FF7/uxtGvblTRnFgs8lA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1lrKIH-000nQ8-87; Thu, 10 Jun 2021 13:00:21 +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 1lrKI6-000nOM-Ed for linux-arm-kernel@lists.infradead.org; Thu, 10 Jun 2021 13:00:11 +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 86B22106F; Thu, 10 Jun 2021 06:00:08 -0700 (PDT) Received: from e113632-lin (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C09813F73D; Thu, 10 Jun 2021 06:00:05 -0700 (PDT) From: Valentin Schneider To: Will Deacon , linux-arm-kernel@lists.infradead.org Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Will Deacon , Catalin Marinas , Marc Zyngier , Greg Kroah-Hartman , Peter Zijlstra , Morten Rasmussen , Qais Yousef , Suren Baghdasaryan , Quentin Perret , Tejun Heo , Johannes Weiner , Ingo Molnar , Juri Lelli , Vincent Guittot , "Rafael J. Wysocki" , Dietmar Eggemann , Daniel Bristot de Oliveira , Mark Rutland , kernel-team@android.com Subject: Re: [PATCH v9 12/20] sched: Allow task CPU affinity to be restricted on asymmetric systems In-Reply-To: <20210608180313.11502-13-will@kernel.org> References: <20210608180313.11502-1-will@kernel.org> <20210608180313.11502-13-will@kernel.org> Date: Thu, 10 Jun 2021 14:00:03 +0100 Message-ID: <875yyldgdo.mognet@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210610_060010_547453_B7BBDF64 X-CRM114-Status: GOOD ( 15.16 ) 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 08/06/21 19:03, Will Deacon wrote: > Asymmetric systems may not offer the same level of userspace ISA support > across all CPUs, meaning that some applications cannot be executed by > some CPUs. As a concrete example, upcoming arm64 big.LITTLE designs do > not feature support for 32-bit applications on both clusters. > > Although userspace can carefully manage the affinity masks for such > tasks, one place where it is particularly problematic is execve() > because the CPU on which the execve() is occurring may be incompatible > with the new application image. In such a situation, it is desirable to > restrict the affinity mask of the task and ensure that the new image is > entered on a compatible CPU. From userspace's point of view, this looks > the same as if the incompatible CPUs have been hotplugged off in the > task's affinity mask. Similarly, if a subsequent execve() reverts to > a compatible image, then the old affinity is restored if it is still > valid. > > In preparation for restricting the affinity mask for compat tasks on > arm64 systems without uniform support for 32-bit applications, introduce > {force,relax}_compatible_cpus_allowed_ptr(), which respectively restrict > and restore the affinity mask for a task based on the compatible CPUs. > > Reviewed-by: Quentin Perret > Signed-off-by: Will Deacon Reviewed-by: Valentin Schneider _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel