11859 need swapgs mitigation
Reviewed by: Robert Mustacchi <rm@fingolfin.org>
Reviewed by: Dan McDonald <danmcd@joyent.com>
Reviewed by: Jerry Jelinek <jerry.jelinek@joyent.com>
Reviewed by: Robert Mustacchi <rm@fingolfin.org>

*** 172,183 ****
          cmpq    %r11, 24(%rsp)
          je      1f
          leaq    tr_brand_sys_sysenter(%rip), %r11
          cmpq    %r11, 24(%rsp)
          jne     2f
! 1:      SWAPGS
! 2:      popq    %r11
  #endif  /* !__xpv */
  
          INTR_PUSH
  #if defined(__xpv)
          movl    $6, %edi
--- 172,184 ----
          cmpq    %r11, 24(%rsp)
          je      1f
          leaq    tr_brand_sys_sysenter(%rip), %r11
          cmpq    %r11, 24(%rsp)
          jne     2f
! 1:      swapgs
! 2:      lfence /* swapgs mitigation */
!         popq    %r11
  #endif  /* !__xpv */
  
          INTR_PUSH
  #if defined(__xpv)
          movl    $6, %edi