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=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 ACAD4C433E0 for ; Tue, 19 May 2020 14:45:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 83CB820825 for ; Tue, 19 May 2020 14:45:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=notmuch.email header.i=@notmuch.email header.b="vtoz3V1h" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729152AbgESOpe (ORCPT ); Tue, 19 May 2020 10:45:34 -0400 Received: from mx.h4ck.space ([159.69.146.50]:37726 "EHLO mx.h4ck.space" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727904AbgESOpb (ORCPT ); Tue, 19 May 2020 10:45:31 -0400 X-Greylist: delayed 430 seconds by postgrey-1.27 at vger.kernel.org; Tue, 19 May 2020 10:45:31 EDT Date: Tue, 19 May 2020 16:38:15 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=notmuch.email; s=mail; t=1589899096; bh=Y9XZYNt+/7HUPB/P7WIrgOb1ARcvi6Rd5XCUCLuyNs0=; h=Date:From:To:Subject; b=vtoz3V1hUuSRbULf8tZ0J8tGKjJrqwfYb70ZRrxExO+2kdpZa+7qRUUSY45v+/0Eg cFMXEB46yGiFATylC/1F7x1vS+gS0VJzbce3RfImbkp7rcB2TYzFa50Z5WCt5eGQT7 yF2KjHu1yQNoGHjGbRVVRagYDr4rjAuzJ00mpylk= From: Andreas Rammhold To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Ricardo Neri , "Eric W. Biederman" , Sergey Senozhatsky , Babu Moger , Kefeng Wang , Jason Yan , Brendan Shanks , linux-kernel@vger.kernel.org Subject: umip: AMD Ryzen 3900X, pagefault after emulate SLDT/SIDT instruction Message-ID: <20200519143815.cpsd2xfx2kl3khsq@wrt> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, I've been running into a weird problem with UMIP on a current Ryzen 3900x with kernel 5.6.11 where a process receives a page fault after the kernel handled the SLDT (or SIDT) instruction (emulation). The program I am running is run through WINE in 32bit mode and tries to figure out if it is running in a VMWare machine by comparing the results of SLDT against well known constants (basically as shown in the [example] linked below). In dmesg I see the following log lines: > [99970.004756] umip: Program.exe[3080] ip:4373fb sp:32f3e0: SIDT instruction cannot be used by applications. > [99970.004757] umip: Program.exe[3080] ip:4373fb sp:32f3e0: For now, expensive software emulation returns the result. > [99970.004758] umip: Program.exe[3080] ip:437415 sp:32f3e0: SLDT instruction cannot be used by applications. Following that the process terminates with a page fault: > Unhandled exception: page fault on read access to 0xffffffff in 32-bit code (0x0000000000437415). Assembly at that address: > 0x0000000000437415: sldt 0xffffffe8(%ebp) 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? On the Ryzen the code executes successfully after setting CONFIG_X86_UMIP=n. I'd love to contriubte a patch but I have no knowledge of the inner workings of how UMIP actually works. Is there anything else I can provide to help debugging/fixing this? Very happy to test patches as well. [example] https://www.aldeid.com/wiki/X86-assembly/Instructions/sldt