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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 E4B31CA9ED0 for ; Fri, 1 Nov 2019 18:24:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BC8C4218AC for ; Fri, 1 Nov 2019 18:24:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572632662; bh=SzUM5NeWAG+E0eqSpj3zuD6ltC8wZE1F+AwKRX2zRSg=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=N/zLM2qIASQ8P03eTkLTKworsTXiAjX5CB0v2puTDUvu44wtadOm3rv8Em9rwWlN6 d5jIFwSdXgINBFxy/3SChGHjlDZ+pKp4txYKlaQDS/XOFD6517VUwJ/UqePBECfNz8 EHKQAyGD3K+gH7vSf1olRSK8u/4ItPOlyWJIuYCc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727409AbfKASYV (ORCPT ); Fri, 1 Nov 2019 14:24:21 -0400 Received: from mail.kernel.org ([198.145.29.99]:57874 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726498AbfKASYU (ORCPT ); Fri, 1 Nov 2019 14:24:20 -0400 Received: from mail-wr1-f52.google.com (mail-wr1-f52.google.com [209.85.221.52]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A1FA021929 for ; Fri, 1 Nov 2019 18:24:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572632659; bh=SzUM5NeWAG+E0eqSpj3zuD6ltC8wZE1F+AwKRX2zRSg=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=r7HrHj9UZqBsFeT98x68brCm5kINTp72KRT74jbUyMQzq0yV8evb8UUFIIoMbzeh+ qQeaa+cCLERZQ67DtNu3WqWqvXhhSkMCnR9LVnzKC9mwX53Jfm8geDhMAG0l33WSLZ JaUTlg8lR0H4FC5pBTu4nfPSv7SgaR9Uu0UhWDWc= Received: by mail-wr1-f52.google.com with SMTP id w18so10509386wrt.3 for ; Fri, 01 Nov 2019 11:24:19 -0700 (PDT) X-Gm-Message-State: APjAAAWTNo0LJ69ynT8L+QqrP+hS4aYB1vY6Q2Ka2FK1X+wxLexhf6Cw UGo+cOEOpxtrJMqfThrLQnphybKmrrWjGhlI8MhqXQ== X-Google-Smtp-Source: APXvYqw0rnlRfwdriPZ576aBq0O+9yfzKHeFxM6ELtsX3pHZailT8JBumH5jVuvvbajKbkN8+GHbNieTjD6qZT7bzCU= X-Received: by 2002:adf:e4c5:: with SMTP id v5mr12220218wrm.106.1572632658034; Fri, 01 Nov 2019 11:24:18 -0700 (PDT) MIME-Version: 1.0 References: <157262960837.2838.17520432516398899751.stgit@naples-babu.amd.com> <157262962352.2838.15656190309312238595.stgit@naples-babu.amd.com> In-Reply-To: <157262962352.2838.15656190309312238595.stgit@naples-babu.amd.com> From: Andy Lutomirski Date: Fri, 1 Nov 2019 11:24:05 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 2/4] kvm: svm: Enable UMIP feature on AMD To: "Moger, Babu" Cc: "tglx@linutronix.de" , "mingo@redhat.com" , "bp@alien8.de" , "hpa@zytor.com" , "pbonzini@redhat.com" , "rkrcmar@redhat.com" , "sean.j.christopherson@intel.com" , "vkuznets@redhat.com" , "wanpengli@tencent.com" , "jmattson@google.com" , "x86@kernel.org" , "joro@8bytes.org" , "luto@kernel.org" , "zohar@linux.ibm.com" , "yamada.masahiro@socionext.com" , "nayna@linux.ibm.com" , "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, Nov 1, 2019 at 10:33 AM Moger, Babu wrote: > > AMD 2nd generation EPYC processors support UMIP (User-Mode Instruction > Prevention) feature. The UMIP feature prevents the execution of certain > instructions if the Current Privilege Level (CPL) is greater than 0. > If any of these instructions are executed with CPL > 0 and UMIP > is enabled, then kernel reports a #GP exception. > > The idea is taken from articles: > https://lwn.net/Articles/738209/ > https://lwn.net/Articles/694385/ > > Enable the feature if supported on bare metal and emulate instructions > to return dummy values for certain cases. What are these cases?