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[209.132.180.67]) by mx.google.com with ESMTP id x18si6716127ejo.78.2019.11.01.13.57.43; Fri, 01 Nov 2019 13:58:06 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=lduYS8WK; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727398AbfKASYU (ORCPT + 99 others); Fri, 1 Nov 2019 14:24:20 -0400 Received: from mail.kernel.org ([198.145.29.99]:57882 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726892AbfKASYU (ORCPT ); Fri, 1 Nov 2019 14:24:20 -0400 Received: from mail-wr1-f44.google.com (mail-wr1-f44.google.com [209.85.221.44]) (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 B7D8421D7D 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=1572632660; bh=SzUM5NeWAG+E0eqSpj3zuD6ltC8wZE1F+AwKRX2zRSg=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=lduYS8WKNuwzfVJBAy2651MpqHBfuuZuVEV3pkKPx+Z3COSomJDwQoMx9IpRfWLpL g7J/hLZM0Il1y8JklXz4kSO9tu6x0ut8M0Ls0MB7NODYprJFREQ/pZzoFBwah/g5qL E2A7OkyIKz8YL4u2Zr/4AuM7hNmPuzKDUNdTzbik= Received: by mail-wr1-f44.google.com with SMTP id v9so10499869wrq.5 for ; Fri, 01 Nov 2019 11:24:19 -0700 (PDT) X-Gm-Message-State: APjAAAVQip09itpghLRrG0lKbfZWpYzeUXDhN+2te+OjvJMIC59IQiwW +Sf5DsW7YGnZFDz+yrZsesqNpSzlnKGopWiEwTQz6w== 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: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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?