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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,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 C6204C433E0 for ; Mon, 15 Jun 2020 18:32:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 93BB320707 for ; Mon, 15 Jun 2020 18:32:04 +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="D0jY9gpN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731323AbgFOScD (ORCPT ); Mon, 15 Jun 2020 14:32:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47306 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729354AbgFOScC (ORCPT ); Mon, 15 Jun 2020 14:32:02 -0400 Received: from merlin.infradead.org (unknown [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2BD56C061A0E for ; Mon, 15 Jun 2020 11:32:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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=0uaXx1a8X6ge6muz2Sp6fD7wbgSxal+3tZhrZaa6Nx0=; b=D0jY9gpNa4VuJV7CCVE0XGTQx+ wFyrLfr7o8wDoY51qJTNQjm/4B8lqrCNzGQDtIaw4ik+p3fchHqc7GxZQo3PPjYkyaFuJN0vv+3BM 2lQuY83HRICjGt/2OvYBHm3yWeok729oCC5gH6Ce1JzaIhM3P6pBkVkSZtPK8xvoWPiuvbFN6y7Wn Urz7U9kmgzIn63lIN4t/iFRfGFOxrO7VZC7rNkYDf7PaemLg1BDQRCIIRd845l7uL243G3Kxz+WFs Tlh3KXfKbIpNqHotyfOur8ysWtNG2ghRlTkgsgoiArC27XGJ1RhR25u1/kKY8q02E0olPt8AwdSSc AroCuvcA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jkttA-0003xc-97; Mon, 15 Jun 2020 18:31:21 +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 5D9C03003E1; Mon, 15 Jun 2020 20:31:16 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 4B487203B815D; Mon, 15 Jun 2020 20:31:16 +0200 (CEST) Date: Mon, 15 Jun 2020 20:31:16 +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: <20200615183116.GD2531@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200615181259.GC13792@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 11:12:59AM -0700, Fenghua Yu wrote: > > I don't get why you need a rdmsr here, or why not having one would > > require a TIF flag. Is that because this MSR is XSAVE/XRSTOR managed? > > My concern is TIF flags are precious (only 3 slots available). Defining > a new TIF flag may be not worth it while rdmsr() can check if PASID > is valid in the MSR. And performance here might not be a big issue > in #GP. > > But if you think using TIF flag is better, I can define a new TIF flag > and maintain it per thread (init 0 when clone()/fork(), set 1 in fixup()). > Then we can avoid using rdmsr() to check valid PASID in the MSR. WHY ?!?! What do you need a TIF flag for?