Date: Tue, 8 Nov 2016 14:16:00 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Cc: Ingo Molnar <mingo@kernel.org>, Thomas Gleixner <tglx@linutronix.de>,
        "H. Peter Anvin" <hpa@zytor.com>, linux-kernel@vger.kernel.org,
        x86@kernel.org, linux-doc@vger.kernel.org,
        Andy Lutomirski <luto@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Borislav Petkov <bp@suse.de>, Brian Gerst <brgerst@gmail.com>,
        Chen Yucong <slaoub@gmail.com>, Chris Metcalf <cmetcalf@mellanox.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Fenghua Yu <fenghua.yu@intel.com>, Huang Rui <ray.huang@amd.com>,
        Jiri Slaby <jslaby@suse.cz>, Jonathan Corbet <corbet@lwn.net>,
        "Michael S . Tsirkin" <mst@redhat.com>,
        Paul Gortmaker <paul.gortmaker@windriver.com>,
        "Ravi V . Shankar" <ravi.v.shankar@intel.com>,
        Vlastimil Babka <vbabka@suse.cz>, Shuah Khan <shuah@kernel.org>
Subject: Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention
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References: <1478585533-19406-1-git-send-email-ricardo.neri-calderon@linux.intel.com>
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On Mon, Nov 07, 2016 at 10:12:09PM -0800, Ricardo Neri wrote:
> There is a caveat, however. Certain applications running in virtual-8086
> mode, such as DOSEMU[1] and Wine[2], want to utilize the SGDT, SIDT and
> SLDT instructions for legitimate reasons. In order to keep such
> applications working, UMIP must be disabled/enabled when entering/exiting
> virtual-8086 mode. 

Would it not be better to emulate these instructions for them? What way
we can verify they're not malicious.