svn commit: r328628 - head/sys/amd64/amd64

[Konstantin Belousov]

Author: kib
Date: Wed Jan 31 16:56:02 2018
New Revision: 328628
URL: https://svnweb.freebsd.org/changeset/base/328628

Log:
  When switching IBRS on, also enable STIBP (Single Thread Indirect
  Branch Predictors) mitigation.
  
  DOcument 336996-001 promises that CPUs which implement IBRS but not
  STIBP silently ignore setting of the bit instead of trapping.
  
  Sponsored by:	The FreeBSD Foundation
  MFC after:	1 week

Modified:
  head/sys/amd64/amd64/support.S

Modified: head/sys/amd64/amd64/support.S
==============================================================================
--- head/sys/amd64/amd64/support.S	Wed Jan 31 16:54:05 2018	(r328627)
+++ head/sys/amd64/amd64/support.S	Wed Jan 31 16:56:02 2018	(r328628)
@@ -875,8 +875,8 @@ ENTRY(handle_ibrs_entry)
 	cmpb	$0,hw_ibrs_active(%rip)
 	je	1f
 	movl	$MSR_IA32_SPEC_CTRL,%ecx
-	movl	$IA32_SPEC_CTRL_IBRS,%eax
-	movl	$IA32_SPEC_CTRL_IBRS>>32,%edx
+	movl	$(IA32_SPEC_CTRL_IBRS|IA32_SPEC_CTRL_STIBP),%eax
+	movl	$(IA32_SPEC_CTRL_IBRS|IA32_SPEC_CTRL_STIBP)>>32,%edx
 	wrmsr
 	movb	$1,PCPU(IBPB_SET)
 	testl	$CPUID_STDEXT_SMEP,cpu_stdext_feature(%rip)