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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,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 D9265C47255 for ; Mon, 11 May 2020 05:03:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A47912137B for ; Mon, 11 May 2020 05:03:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589173403; bh=AEQ5/eHF4mOqL/y16T898LganyocNlGAK0Fzmso4HzU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=ZTdKv/nDgWa+6cDBohA4s96fgDkgRfDCVsd7gaTjQ304Of3mhrGBDdjko7vj7eWwq xNZwFyBcWf4H5WDX9aEZHOZKcpbFE3CBkyTgTcMETqsFp2ANM4CUHQqmwNRPhXjeR/ bRYViSNLU2oDhyKbnpuEVgbQyd0No7+6qKsy6kuo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727927AbgEKFDX (ORCPT ); Mon, 11 May 2020 01:03:23 -0400 Received: from mail.kernel.org ([198.145.29.99]:47754 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726013AbgEKFDW (ORCPT ); Mon, 11 May 2020 01:03:22 -0400 Received: from localhost (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1AAE62082E; Mon, 11 May 2020 05:03:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589173402; bh=AEQ5/eHF4mOqL/y16T898LganyocNlGAK0Fzmso4HzU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=F9HiS8pWarfCpH7Ng0cm9R9PYx1ieS/AWHG+N8Y7CCrLII34xmqET1r7qbTQXyGpi vDsjQ1tDTzEvSmfFo7kyoo7F2C5ka95CW9qiVZygzfum7+A2L2WZd70FhFiaetZlao +6y1HWIgdnjcn7XkeJQOBMBz5/ofGjPIqlE9Dg9Q= Date: Mon, 11 May 2020 01:03:21 -0400 From: Sasha Levin To: Andi Kleen Cc: Vegard Nossum , linux-kernel@vger.kernel.org, tglx@linutronix.de, luto@kernel.org, tony.luck@intel.com, chang.seok.bae@intel.com Subject: Re: [PATCH v10 00/18] Enable FSGSBASE instructions Message-ID: <20200511050321.GO13035@sasha-vm> References: <20200423232207.5797-1-sashal@kernel.org> <5a6a0ef5-4dfc-d0b1-9181-5df4211cfcd9@oracle.com> <20200511004842.GJ3538@tassilo.jf.intel.com> <20200511005028.GA226400@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20200511005028.GA226400@tassilo.jf.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 10, 2020 at 05:50:28PM -0700, Andi Kleen wrote: >> So this is a check that checks if you're running in user mode if >> you have a debug trap with single step, but somehow it triggered >> for a user segment. >> >> Probably the regs got corrupted. >> >> Sasha, I suspect you're missing a mov %rsp,%rdi somewhere in the >> debug entry path that sets up the regs argument for the C code. > >... Ah never mind. Thomas has a better explanation. FWIW, this series was heavily tested for the past few months to the point that we're comfortable in enabling it for 3rd party users on Azure: https://bugs.launchpad.net/ubuntu/+source/linux-azure/+bug/1877425. -- Thanks, Sasha