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

[Paolo Bonzini]

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
better.

Paolo