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    Subject[RFC PATCH 09/16] x86/split_lock: Add CONFIG to control #AC for split lock at boot time
    Date
    User wants to specify how to set up #AC for split lock at boot time.

    CONFIG_SPLIT_LOCK_AC_ENABLE_DEFAULT is added to control split
    lock setting at boot time.

    Default value is 2: Don't explicitly enable or disable #AC for split lock.
    Inherit setting of #AC for split lock from firmware.

    Value 0 to explicitly disable split lock at boot time.

    Value 1 to explicitly enable split lock at boot time.

    Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
    ---
    arch/x86/Kconfig | 14 ++++++++++++++
    arch/x86/kernel/cpu/test_ctl.c | 12 ++++++++++++
    2 files changed, 26 insertions(+)

    diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
    index 043cde9a9b08..1d0dcd6fa69a 100644
    --- a/arch/x86/Kconfig
    +++ b/arch/x86/Kconfig
    @@ -461,6 +461,20 @@ config SPLIT_LOCK_AC

    Say N if unsure.

    +config SPLIT_LOCK_AC_ENABLE_DEFAULT
    + int "#AC for split lock enable value (0-2) at boot time"
    + range 0 2
    + default "2"
    + depends on SPLIT_LOCK_AC
    + help
    + Set #AC for split lock enable default value at boot time
    + 0: Explicitly disable #AC for split lock at boot time.
    + 1: Explicitly enable #AC for split lock at boot time.
    + 2: Don't explicitly enable or disable #AC for split lock.
    + Inherit setting of #AC for split lock from firmware.
    +
    + Leave this to the default value of 2 if you are unsure.
    +
    if X86_32
    config X86_BIGSMP
    bool "Support for big SMP systems with more than 8 CPUs"
    diff --git a/arch/x86/kernel/cpu/test_ctl.c b/arch/x86/kernel/cpu/test_ctl.c
    index 82440740b2b9..a2f84fcd4da1 100644
    --- a/arch/x86/kernel/cpu/test_ctl.c
    +++ b/arch/x86/kernel/cpu/test_ctl.c
    @@ -21,6 +21,7 @@

    #define DISABLE_SPLIT_LOCK_AC 0
    #define ENABLE_SPLIT_LOCK_AC 1
    +#define INHERIT_SPLIT_LOCK_AC_FIRMWARE 2

    /* After disabling #AC for split lock in handler, re-enable it 1 msec later. */
    #define reenable_split_lock_delay msecs_to_jiffies(1)
    @@ -71,6 +72,17 @@ void detect_split_lock_ac(void)
    split_lock_ac_firmware = ENABLE_SPLIT_LOCK_AC;
    else
    split_lock_ac_firmware = DISABLE_SPLIT_LOCK_AC;
    +
    + /*
    + * By default configuration, kernel inherits firmware split lock
    + * setting. Kernel can be configured to explicitly enable or disable
    + * #AC for split lock to override firmware setting.
    + */
    + if (CONFIG_SPLIT_LOCK_AC_ENABLE_DEFAULT ==
    + INHERIT_SPLIT_LOCK_AC_FIRMWARE)
    + split_lock_ac_kernel = split_lock_ac_firmware;
    + else
    + split_lock_ac_kernel = CONFIG_SPLIT_LOCK_AC_ENABLE_DEFAULT;
    }

    static void _setup_split_lock(int split_lock_ac_val)
    --
    2.5.0
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