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/Kconfig | |
| 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/Kconfig')
| -rw-r--r-- | arch/s390/Kconfig | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index f5a154d438ee..02eb7a91ad35 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -704,6 +704,23 @@ config SECCOMP If unsure, say Y. +config KERNEL_NOBP + def_bool n + prompt "Enable modified branch prediction for the kernel by default" + help + If this option is selected the kernel will switch to a modified + branch prediction mode if the firmware interface is available. + The modified branch prediction mode improves the behaviour in + regard to speculative execution. + + With the option enabled the kernel parameter "nobp=0" or "nospec" + can be used to run the kernel in the normal branch prediction mode. + + With the option disabled the modified branch prediction mode is + enabled with the "nobp=1" kernel parameter. + + If unsure, say N. + endmenu menu "Power Management" |