Received: by 2002:a05:6a11:4021:0:0:0:0 with SMTP id ky33csp2180907pxb; Fri, 24 Sep 2021 23:38:52 -0700 (PDT) X-Google-Smtp-Source: ABdhPJz88vepzU+pinavduryj04TNQkPRQKr1sWBFPiKnJbxfCueTm/8/HHU3t+EjXnveCnOBjkc X-Received: by 2002:a17:906:fc7:: with SMTP id c7mr16026589ejk.333.1632551932491; Fri, 24 Sep 2021 23:38:52 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1632551932; cv=none; d=google.com; s=arc-20160816; b=dNqiKwvnMsiDEKfvUKZ5foi7P7b7cEHKLGjE/zHbNeJg6DzsujMaKOvFP7B0Onc11k rPMMdr8hQEhKZoa2JJdnEnvr+A7iJvpw689NNKwn8he1iwCI9tka4zILt8w2FO351Xl7 Odmqny0nzDEBw3ri0n12/rumRSMQLJn7cAxOqwhvTcmXRu8HDU68BGFPwWnPUWVUw9MK jhrnzyJBO/lw2WRPsVvz2pOcyOFBqYOnmnqg+kqLmPUrCQwRS9sVi2/NiSnvcDtiH6o0 ahjvStFU8gZtmDtvROBakIrMBzIAjkzTWPBbf6ILrhYp4rg33xsI6J1wNcrAB3hl7jMg ZUqQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:in-reply-to:content-disposition:mime-version :references:message-id:subject:cc:to:from:date; bh=EBnPPaWinxw6ZvNXIhI19vvwzl3c/yOl8iPK5whlm0g=; b=NpZ5EPf0JOMW9E6tUzW4LRuwscIO6qb4mjDDzDHB1ENExzSz8iAh49bxHvRQZ49jQ7 C6l/6/n+G92lomBtzjp1Z12x3qMkjWD0giBSH6JDL3NQxbSWiXi/7f2brta/PkL1VsH0 BAvSkXqtmB/7RBH1z5WFT8LEesw0wwa4rJjZIglGKCs7oHH6MmO8efXv5Knte8ocLjaI V1jSZqoxJpAqZqrrHZW+VPQ2p3+GsjZTEMm9g/5YQkw8SyKiSzRj5t0Qv5rlyGNpUHMU G0UQ5rIFvDcQvxncMN+TiWr8bgZIU8dRolJJOcqkR02TFsTTfjUcXlgXqhjyfBfFyhDX zD6w== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id mp19si2966886ejc.630.2021.09.24.23.38.29; Fri, 24 Sep 2021 23:38:52 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237994AbhIXXNc (ORCPT + 99 others); Fri, 24 Sep 2021 19:13:32 -0400 Received: from mga01.intel.com ([192.55.52.88]:51291 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230021AbhIXXNc (ORCPT ); Fri, 24 Sep 2021 19:13:32 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10117"; a="246659417" X-IronPort-AV: E=Sophos;i="5.85,321,1624345200"; d="scan'208";a="246659417" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Sep 2021 16:11:58 -0700 X-IronPort-AV: E=Sophos;i="5.85,321,1624345200"; d="scan'208";a="559859753" Received: from agluck-desk2.sc.intel.com (HELO agluck-desk2.amr.corp.intel.com) ([10.3.52.146]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Sep 2021 16:11:58 -0700 Date: Fri, 24 Sep 2021 16:11:57 -0700 From: "Luck, Tony" To: Andy Lutomirski Cc: Thomas Gleixner , Fenghua Yu , Ingo Molnar , Borislav Petkov , "Peter Zijlstra (Intel)" , Dave Hansen , Lu Baolu , Joerg Roedel , Josh Poimboeuf , Dave Jiang , Jacob Jun Pan , Raj Ashok , "Shankar, Ravi V" , iommu@lists.linux-foundation.org, the arch/x86 maintainers , Linux Kernel Mailing List Subject: Re: [PATCH 5/8] x86/mmu: Add mm-based PASID refcounting Message-ID: References: <20210920192349.2602141-1-fenghua.yu@intel.com> <20210920192349.2602141-6-fenghua.yu@intel.com> <87y27nfjel.ffs@tglx> <87o88jfajo.ffs@tglx> <87k0j6dsdn.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 24, 2021 at 04:03:53PM -0700, Andy Lutomirski wrote: > 1. The context switch code needs to resync PASID. Unfortunately, this adds some overhead to every context switch, although a static_branch could minimize it for non-PASID users. Any solution that adds to context switch time isn't going to meet the definition of "perfect" either. -Tony