diff options
| author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2018-04-27 07:36:45 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-04-29 11:31:59 +0200 |
| commit | 07f65a834a814fb1a1b428b26a671f9196031b60 (patch) | |
| tree | 85a2a7d1e4be13440300bf0769eb273fe2216e40 /arch/s390/kernel/early.c | |
| parent | 46bd2c0ffd5cf7642a9dd87b294be9d2e51adb69 (diff) | |
s390: add options to change branch prediction behaviour for the kernel
[ Upstream commit d768bd892fc8f066cd3aa000eb1867bcf32db0ee ]
Add the PPA instruction to the system entry and exit path to switch
the kernel to a different branch prediction behaviour. The instructions
are added via CPU alternatives and can be disabled with the "nospec"
or the "nobp=0" kernel parameter. If the default behaviour selected
with CONFIG_KERNEL_NOBP is set to "n" then the "nobp=1" parameter can be
used to enable the changed kernel branch prediction.
Acked-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/s390/kernel/early.c')
| -rw-r--r-- | arch/s390/kernel/early.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/s390/kernel/early.c b/arch/s390/kernel/early.c index 171aaa221e4b..0c7a7d5d95f1 100644 --- a/arch/s390/kernel/early.c +++ b/arch/s390/kernel/early.c @@ -302,6 +302,8 @@ static noinline __init void setup_facility_list(void) memcpy(S390_lowcore.alt_stfle_fac_list, S390_lowcore.stfle_fac_list, sizeof(S390_lowcore.alt_stfle_fac_list)); + if (!IS_ENABLED(CONFIG_KERNEL_NOBP)) + __clear_facility(82, S390_lowcore.alt_stfle_fac_list); } static __init void detect_diag9c(void) |