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
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