There is an error in file cpu\proc_ctrl.cc
When sysret instruction switch to long mode it should make CS(PL)=3 and SS(PL)=3.
Line 2213 is:
parse_selector((Bit16u)((MSR_STAR >> 48) + 8),
&BX_CPU_THIS_PTR sregs[BX_SEG_REG_SS].selector);
I think it should be:
parse_selector((Bit16u)(((MSR_STAR >> 48) + 8) | 3 ),
&BX_CPU_THIS_PTR sregs[BX_SEG_REG_SS].selector);
For CS selector it's ok.
Thanks, fixed in CVS