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| author |   Martin Schwidefsky <schwidefsky@de.ibm.com> | 2018-01-16 07:11:45 +0100 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2018-02-05 13:49:17 +0100 |
| commit | d768bd892fc8f066cd3aa000eb1867bcf32db0ee (patch) | |
| tree | 73856bebc552b175d71bef6859824d7ca8d8e051 /arch/s390/kernel/early.c | |
| parent | s390/alternative: use a copy of the facility bit mask (diff) | |
| download | linux-dev-d768bd892fc8f066cd3aa000eb1867bcf32db0ee.tar.xz linux-dev-d768bd892fc8f066cd3aa000eb1867bcf32db0ee.zip | |
s390: add options to change branch prediction behaviour for the kernel
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>
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 510f2183a7e7..ac707a9f729e 100644 --- a/arch/s390/kernel/early.c +++ b/arch/s390/kernel/early.c @@ -196,6 +196,8 @@ 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) |