From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Subject: Re: [v6 PATCH 00/21] x86: Enable User-Mode Instruction Prevention
Date: Wed, 08 Mar 2017 17:15:22 -0800
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To: Andy Lutomirski <luto@amacapital.net>
Cc: Stas Sergeev <stsp@list.ru>, Ingo Molnar <mingo@redhat.com>, Thomas Gleixner <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>, Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@suse.de>, Peter Zijlstra <peterz@infradead.org>, Andrew Morton <akpm@linux-foundation.org>, Brian Gerst <brgerst@gmail.com>, Chris Metcalf <cmetcalf@mellanox.com>, Dave Hansen <dave.hansen@linux.intel.com>, Paolo Bonzini <pbonzini@redhat.com>, Liang Z Li <liang.z.li@intel.com>, Masami Hiramatsu <mhiramat@kernel.org>, 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>, Vlastimil Babka <vbabka@suse.cz>, Chen Yucong <slaoub@gmail.com>

On Wed, 2017-03-08 at 08:46 -0800, Andy Lutomirski wrote:
> On Wed, Mar 8, 2017 at 8:29 AM, Stas Sergeev <stsp@list.ru> wrote:
> > 08.03.2017 19:06, Andy Lutomirski пишет:
> >>
> >> On Wed, Mar 8, 2017 at 6:08 AM, Stas Sergeev <stsp@list.ru> wrote:
> >>>
> >>> 08.03.2017 03:32, Ricardo Neri пишет:
> >>>>
> >>>> These are the instructions covered by UMIP:
> >>>> * SGDT - Store Global Descriptor Table
> >>>> * SIDT - Store Interrupt Descriptor Table
> >>>> * SLDT - Store Local Descriptor Table
> >>>> * SMSW - Store Machine Status Word
> >>>> * STR - Store Task Register
> >>>>
> >>>> This patchset initially treated tasks running in virtual-8086
> mode as a
> >>>> special case. However, I received clarification that DOSEMU[8]
> does not
> >>>> support applications that use these instructions.
> >>
> >> Can you remind me what was special about it?  It looks like you
> still
> >> emulate them in v8086 mode.
> >
> > Indeed, sorry, I meant prot mode here. :)
> > So I wonder what was cited to be special about v86.

Initially my patches disabled UMIP on virtual-8086 instructions, without
regards of protected mode (i.e., UMIP was always enabled). I didn't have
emulation at the time. Then, I added emulation code that now covers
protected and virtual-8086 modes. I guess it is not special anymore.

Thanks and BR,
Ricardo