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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 78B4DC433E0 for ; Mon, 15 Jun 2020 20:17:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 565AB207D4 for ; Mon, 15 Jun 2020 20:17:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731606AbgFOURi (ORCPT ); Mon, 15 Jun 2020 16:17:38 -0400 Received: from mga11.intel.com ([192.55.52.93]:10830 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731106AbgFOURh (ORCPT ); Mon, 15 Jun 2020 16:17:37 -0400 IronPort-SDR: uwNPJe8/Z67Ss4B/NnzO7MxyFXppBkMO4JErzQvFIMsoHgddoKROjZuM1MHeQ28bz0TRAn5YlA RcjReoUGF/Yw== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Jun 2020 13:17:36 -0700 IronPort-SDR: bBvH2ZJYn5YJMJRfAqP3otKSEI1MNvgA+6c1UKYREDg7BecOd1t0qIyR3pPh+HR14Zjkx/e/PR UvvQUKw6T4WA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,516,1583222400"; d="scan'208";a="351478020" Received: from romley-ivt3.sc.intel.com ([172.25.110.60]) by orsmga001.jf.intel.com with ESMTP; 15 Jun 2020 13:17:35 -0700 Date: Mon, 15 Jun 2020 13:17:35 -0700 From: Fenghua Yu To: Peter Zijlstra Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , H Peter Anvin , David Woodhouse , Lu Baolu , Frederic Barrat , Andrew Donnellan , Felix Kuehling , Joerg Roedel , Dave Hansen , Tony Luck , Ashok Raj , Jacob Jun Pan , Dave Jiang , Yu-cheng Yu , Sohil Mehta , Ravi V Shankar , linux-kernel , x86 , iommu@lists.linux-foundation.org, amd-gfx , linuxppc-dev Subject: Re: [PATCH v2 12/12] x86/traps: Fix up invalid PASID Message-ID: <20200615201735.GE13792@romley-ivt3.sc.intel.com> References: <1592008893-9388-1-git-send-email-fenghua.yu@intel.com> <1592008893-9388-13-git-send-email-fenghua.yu@intel.com> <20200615075649.GK2497@hirez.programming.kicks-ass.net> <20200615154854.GB13792@romley-ivt3.sc.intel.com> <20200615160357.GA2531@hirez.programming.kicks-ass.net> <20200615181259.GC13792@romley-ivt3.sc.intel.com> <20200615183116.GD2531@hirez.programming.kicks-ass.net> <20200615185529.GD13792@romley-ivt3.sc.intel.com> <20200615190928.GJ2531@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200615190928.GJ2531@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Peter, On Mon, Jun 15, 2020 at 09:09:28PM +0200, Peter Zijlstra wrote: > On Mon, Jun 15, 2020 at 11:55:29AM -0700, Fenghua Yu wrote: > > > Or do you suggest to add a random new flag in struct thread_info instead > > of a TIF flag? > > Why thread_info? What's wrong with something simple like the below. It > takes a bit from the 'strictly current' flags word. > > > diff --git a/include/linux/sched.h b/include/linux/sched.h > index b62e6aaf28f0..fca830b97055 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -801,6 +801,9 @@ struct task_struct { > /* Stalled due to lack of memory */ > unsigned in_memstall:1; > #endif > +#ifdef CONFIG_PCI_PASID > + unsigned has_valid_pasid:1; > +#endif > > unsigned long atomic_flags; /* Flags requiring atomic access. */ > > diff --git a/kernel/fork.c b/kernel/fork.c > index 142b23645d82..10b3891be99e 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -955,6 +955,10 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node) > tsk->use_memdelay = 0; > #endif > > +#ifdef CONFIG_PCI_PASID > + tsk->has_valid_pasid = 0; > +#endif > + > #ifdef CONFIG_MEMCG > tsk->active_memcg = NULL; > #endif The PASID MSR is x86 specific although PASID is PCIe concept and per-mm. Checking if the MSR has valid PASID (bit31=1) is an x86 specifc work. The flag should be cleared in cloned()/forked() and is only set and read in fixup() in x86 #GP for heuristic. It's not used anywhere outside of x86. That's why we think the flag should be in x86 struct thread_info instead of in generice struct task_struct. Please advice. Thanks. -Fenghua