On Tue, 2016-11-08 at 17:52 +0100, Thomas Gleixner wrote: > On Tue, 8 Nov 2016, Andy Lutomirski wrote: > > On Tue, Nov 8, 2016 at 5:16 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > 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. > > > > Forget malice -- if they are really needed for some silly vm86-using > > program, let's trap them and emulate them so they return dummy values. > > handle_vm86_fault() already does instruction emulation, so adding the few > bits there is the right thing to do. Then we just can enable UMIP > unconditionally and be done with it. Ah. I didn't think about that. It make sense to me. I will rework this series with this approach. > > Thanks, > > tglx -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
