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=-3.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 66ECCC433E0 for ; Mon, 15 Jun 2020 21:54:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3FDF92071A for ; Mon, 15 Jun 2020 21:54:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="LSD5JPxk" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726416AbgFOVyX (ORCPT ); Mon, 15 Jun 2020 17:54:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726044AbgFOVyW (ORCPT ); Mon, 15 Jun 2020 17:54:22 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C4D11C061A0E for ; Mon, 15 Jun 2020 14:54:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=UqgtxJyXNkDi+0YvkljyuVgWArZfOIPs0r0FfUbx9gk=; b=LSD5JPxkLs9AcgxjDG0aMNn4Jw ezfvCVV68rnipIJFxD+zL54W/CRA6wrZNbxCvhOd6Mz7U+W2zW4wsDHPxzgoKaFhBJD/n3Zjy7JMH 6um/p8pHUjP0zSfu0a9ckO4OA4+X/O4P3ODIkp052EI+ae0Ov9jbkACGWf3ReTnI7WWUn/tC+xmZu 8eVWcz2CKDjEdXIdRpMjJ2J6ThhGnBBtRaM5AQ9Suas4+u33Wd8ORKSREHPhi7o4HYYJe3r11ww+v 4P0e1eL/oZSJ5XVvmaCITCLoQ0QQtgLOV5+U/+4qVP+6DsaxaqIHRyoONo5PFTrbUO1kt2FFz1wcK NP6xRd8w==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jkx3F-0001qx-4m; Mon, 15 Jun 2020 21:53:57 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 7C474301A32; Mon, 15 Jun 2020 23:53:53 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 6897E2BDC14F9; Mon, 15 Jun 2020 23:53:53 +0200 (CEST) Date: Mon, 15 Jun 2020 23:53:53 +0200 From: Peter Zijlstra To: Fenghua Yu 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: <20200615215353.GH2514@hirez.programming.kicks-ass.net> 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> <20200615201735.GE13792@romley-ivt3.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200615201735.GE13792@romley-ivt3.sc.intel.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 15, 2020 at 01:17:35PM -0700, Fenghua Yu wrote: > 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. I don't think anybody really cares, it's just one bit, we have plenty left. On x86_64 there's a u32 sized alignment hole in thread_info, also we don't use the upper 32bit of thread_info::flags, however using those would still mean you have to use atomic ops, which you really don't need.