svn commit: r334150 - stable/11/sys/amd64/amd64

[Konstantin Belousov]

Author: kib
Date: Thu May 24 11:59:33 2018
New Revision: 334150
URL: https://svnweb.freebsd.org/changeset/base/334150

Log:
  MFC r334003:
  Preserve other bits in IA32_SPEC_CTL MSR when changing the IBRS and
  STIBP states.
  
  Approved by:	re (gjb)

Modified:
  stable/11/sys/amd64/amd64/support.S
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/sys/amd64/amd64/support.S
==============================================================================
--- stable/11/sys/amd64/amd64/support.S	Thu May 24 11:02:21 2018	(r334149)
+++ stable/11/sys/amd64/amd64/support.S	Thu May 24 11:59:33 2018	(r334150)
@@ -849,8 +849,9 @@ ENTRY(handle_ibrs_entry)
 	cmpb	$0,hw_ibrs_active(%rip)
 	je	1f
 	movl	$MSR_IA32_SPEC_CTRL,%ecx
-	movl	$(IA32_SPEC_CTRL_IBRS|IA32_SPEC_CTRL_STIBP),%eax
-	movl	$(IA32_SPEC_CTRL_IBRS|IA32_SPEC_CTRL_STIBP)>>32,%edx
+	rdmsr
+	orl	$(IA32_SPEC_CTRL_IBRS|IA32_SPEC_CTRL_STIBP),%eax
+	orl	$(IA32_SPEC_CTRL_IBRS|IA32_SPEC_CTRL_STIBP)>>32,%edx
 	wrmsr
 	movb	$1,PCPU(IBPB_SET)
 	testl	$CPUID_STDEXT_SMEP,cpu_stdext_feature(%rip)
@@ -863,8 +864,9 @@ ENTRY(handle_ibrs_exit)
 	cmpb	$0,PCPU(IBPB_SET)
 	je	1f
 	movl	$MSR_IA32_SPEC_CTRL,%ecx
-	xorl	%eax,%eax
-	xorl	%edx,%edx
+	rdmsr
+	andl	$~(IA32_SPEC_CTRL_IBRS|IA32_SPEC_CTRL_STIBP),%eax
+	andl	$~((IA32_SPEC_CTRL_IBRS|IA32_SPEC_CTRL_STIBP)>>32),%edx
 	wrmsr
 	movb	$0,PCPU(IBPB_SET)
 1:	ret
@@ -878,8 +880,9 @@ ENTRY(handle_ibrs_exit_rs)
 	pushq	%rdx
 	pushq	%rcx
 	movl	$MSR_IA32_SPEC_CTRL,%ecx
-	xorl	%eax,%eax
-	xorl	%edx,%edx
+	rdmsr
+	andl	$~(IA32_SPEC_CTRL_IBRS|IA32_SPEC_CTRL_STIBP),%eax
+	andl	$~((IA32_SPEC_CTRL_IBRS|IA32_SPEC_CTRL_STIBP)>>32),%edx
 	wrmsr
 	popq	%rcx
 	popq	%rdx