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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS 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 EF649C433DF for ; Wed, 20 May 2020 01:04:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AF949207D8 for ; Wed, 20 May 2020 01:04:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=notmuch.email header.i=@notmuch.email header.b="NJpU64f0" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728275AbgETBEV (ORCPT ); Tue, 19 May 2020 21:04:21 -0400 Received: from mx.h4ck.space ([159.69.146.50]:58672 "EHLO mx.h4ck.space" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726318AbgETBEU (ORCPT ); Tue, 19 May 2020 21:04:20 -0400 Date: Wed, 20 May 2020 03:04:18 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=notmuch.email; s=mail; t=1589936658; bh=SXL42srFoPlaa2GUG3aQEU4fKva96clfFImQwvvj0kk=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=NJpU64f086GykurTVLJgzZg2h6QJW6hyh4o4awavfBwOCyTWlGRUa9QnS4i1WonMw LKgv1wirpX6uWaTATrjPhiaMog7MfV88X7cAFHU6iqgAoY/GOS2RzDZXNU2RCBr3A9 cS4VU71DxdVi8Ap5My4DjUSGvn/An5DwMOEEqlf4= From: andi@notmuch.email To: Ricardo Neri Cc: Brendan Shanks , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , "Eric W. Biederman" , Sergey Senozhatsky , Babu Moger , Kefeng Wang , Jason Yan , linux-kernel@vger.kernel.org Subject: Re: umip: AMD Ryzen 3900X, pagefault after emulate SLDT/SIDT instruction Message-ID: <20200520010418.ippljxawcwrbp6o2@wrt> References: <20200519143815.cpsd2xfx2kl3khsq@wrt> <2330FAB4-A6CE-49E7-921C-B7D55763BDED@codeweavers.com> <20200519194320.GA25138@ranerica-svr.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200519194320.GA25138@ranerica-svr.sc.intel.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12:43 19.05.20, Ricardo Neri wrote: > > > Running the same executable on the exact same kernel (and userland) but > > > on a Intel i7-8565U doesn't crash at this point. I am guessing the > > > emulation is supposed to do something different on AMD CPUs? > > I am surprised you don't see it on the Intel processor. Maybe it does > not have UMIP. Do you see umip when you do > > $ grep umip /proc/cpuinfo Indeed it doesn't ahve the feature. I would have assumed that it is recent enough. Apparently not. > > > On the Ryzen the code executes successfully after setting CONFIG_X86_UMIP=n. > > > > Hi Andreas, > > > > The problem is that the kernel does not emulate/spoof the SLDT instruction, only SGDT, SIDT, and SMSW. > > SLDT and STR weren't thought to be commonly used, so emulation/spoofing wasn’t added. > > In the last few months I have seen reports of one or two (32-bit) Windows games that use SLDT though. > > Can you share more information about the application you’re running? > > > > Maybe the best path is to add kernel emulation/spoofing for SLDT and STR on 32 and 64-bit, just to cover all the cases. It should be a pretty simple patch, I’ll start working on it. > > I have a patch for this already that I wrote for testing purposes: > > https://github.com/ricardon/tip/commit/1692889cb3f8accb523d44b682458e234b93be50 > > Perhaps it can be used as a starting point? Not sure what the spoofing > value should be, though. Perhaps 0? I am not entirely sure what it should return in the general case. My assumption is that 0 might work. Maybe making it configurable like with the other UMIP constants that I saw? I'll give the patch a shot and try to figure out what the authors of the code have to say about it.