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s390: run user space and KVM guests with modified branch prediction

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Define TIF_ISOLATE_BP and TIF_ISOLATE_BP_GUEST and add the necessary
plumbing in entry.S to be able to run user space and KVM guests with
limited branch prediction.

To switch a user space process to limited branch prediction the
s390_isolate_bp() function has to be call, and to run a vCPU of a KVM
guest associated with the current task with limited branch prediction
call s390_isolate_bp_guest().

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky
2018-01-16 07:36:46 +01:00
parent d768bd892f
commit 6b73044b2b
4 changed files with 71 additions and 5 deletions
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18
arch/s390/kernel/processor.c
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@@ -197,3 +197,21 @@ const struct seq_operations cpuinfo_op = {
.stop = c_stop,
.show = show_cpuinfo,
};
int s390_isolate_bp(void)
{
if (!test_facility(82))
return -EOPNOTSUPP;
set_thread_flag(TIF_ISOLATE_BP);
return 0;
}
EXPORT_SYMBOL(s390_isolate_bp);
int s390_isolate_bp_guest(void)
{
if (!test_facility(82))
return -EOPNOTSUPP;
set_thread_flag(TIF_ISOLATE_BP_GUEST);
return 0;
}
EXPORT_SYMBOL(s390_isolate_bp_guest);