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)
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