Re: [Kernel BUG?] SMSW operation get success on UMIP KVM guest

From: Paolo Bonzini
Date: Mon Jul 01 2019 - 13:30:56 EST

On 01/07/19 16:53, Ricardo Neri wrote:
>> (*) before the x86 people jump at me, this won't happen unless you
>> explicitly pass an option to QEMU, such as "-cpu host,+umip". :) The
>> incorrect emulation of SMSW when CR4.UMIP=1 is why.
> Paolo, what do you mean by the incorrect emulation of SMSW?

When KVM tries to emulate UMIP on a system that doesn't have it, SMSW
won't cause a #GP. The processor is simply not able to trap to the
hypervisor on SMSW (unlike SGDT/SIDT/SLDT/STR), so it's impossible to do