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=-5.9 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 38EADC47082 for ; Thu, 3 Jun 2021 17:31:42 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [140.211.166.137]) (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 C02A6613AD for ; Thu, 3 Jun 2021 17:31:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C02A6613AD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id 8A585405A7; Thu, 3 Jun 2021 17:31:41 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id y0P3HpiPfEmU; Thu, 3 Jun 2021 17:31:40 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp4.osuosl.org (Postfix) with ESMTP id 4AB71404FE; Thu, 3 Jun 2021 17:31:40 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 0D36EC000E; Thu, 3 Jun 2021 17:31:40 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [IPv6:2605:bc80:3010::137]) by lists.linuxfoundation.org (Postfix) with ESMTP id 18BB9C0001 for ; Thu, 3 Jun 2021 17:31:39 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id E4CC3405A7 for ; Thu, 3 Jun 2021 17:31:38 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id oT0UCx3_mj5D for ; Thu, 3 Jun 2021 17:31:38 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp4.osuosl.org (Postfix) with ESMTPS id 380C4404FE for ; Thu, 3 Jun 2021 17:31:38 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 14028600EF; Thu, 3 Jun 2021 17:31:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1622741497; bh=CYn3EZTKJSh4MDX20btEjoQc2gajFSLKSEiCLpjOtyY=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=UAfQrL/7OJGOkvO3MmOhUAvtCeD/mHVyyYbGmRCp6YswxdYsZq38j7rp2gh0G4bhW L98RJBLj9EVzi9azrc/Av2CuAvjOzYOtDhxzLz819aT/E3Wm/eBofItZHJb+he3jFe gMhfZD35ABXCWbxTpPJMR4U3aAkVMD3MMzM9724UXggGSCuSLk95MHApGY0Vrnq435 /Ql2LfZn30+bGoyfvo7j9QMIrgh83CLd7NlfSlJQORtxTenr6qxgIoe3eK8FcA/f0f WvyPBLVV1JHqbQ0MGwJOd3CStKpYjqJOFOiOhGphNIJ8I8AErF1fedToDDc5a7AOi3 wPMrxiTypLfQQ== Subject: Re: [PATCH] x86/cpufeatures: Force disable X86_FEATURE_ENQCMD and remove update_pasid() To: "Luck, Tony" , Thomas Gleixner , Borislav Petkov References: <1600187413-163670-1-git-send-email-fenghua.yu@intel.com> <1600187413-163670-10-git-send-email-fenghua.yu@intel.com> <87mtsd6gr9.ffs@nanos.tec.linutronix.de> <87y2bv438p.ffs@nanos.tec.linutronix.de> <36866b38ec92425b879881a88acf547b@intel.com> From: Andy Lutomirski Message-ID: Date: Thu, 3 Jun 2021 10:31:36 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <36866b38ec92425b879881a88acf547b@intel.com> Content-Language: en-US Cc: "Yu, Fenghua" , Randy Dunlap , "Jiang, Dave" , "Raj, Ashok" , "Shankar, Ravi V" , Jean-Philippe Brucker , Peter Zijlstra , x86 , linux-kernel , Christoph Hellwig , "Hansen, Dave" , "iommu@lists.linux-foundation.org" , Ingo Molnar , "Pan, Jacob jun" , H Peter Anvin , David Woodhouse X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On 6/2/21 1:37 PM, Luck, Tony wrote: >>> ... so on a PASID system, your trivial reproducer would theoretically >>> fire the same way and corrupt FPU state just as well. >> >> This is worse and you can't selftest it because the IPI can just hit in >> the middle of _any_ FPU state operation and corrupt state. > > That sounds like we should abandon the "IPI all the other threads > to force enable the PASID for them" approach. It would just be a > nightmare of papering over cracks when the IPI was delivered at > some inconvenient moment when the recipient was in the middle > of touching xsave state. > > I've told Fenghua to dig out the previous iteration of this patch where > the plan was to lazily fix the PASID_MSR in other threads in the #GP > handler. Blech. Also this won't work for other PASID-like features. I have a half-written patch to fix this up for real. Stay tuned. > Seems like a better direction than trying to fix the IPI method. The virtualization > folks will like this way more because IPI in guest causes a couple of VMEXIT > so is somewhat expensive. It happens at most once per PASID-using process. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu