Re: [PATCH v17] x86/split_lock: Enable split lock detection by kernel

[Thomas Gleixner]

"Luck, Tony" <tony.luck@xxxxxxxxx> writes:
> +static bool __sld_msr_set(bool on)
> +{
> +	u64 test_ctrl_val;
> +
> +	if (rdmsrl_safe(MSR_TEST_CTRL, &test_ctrl_val))
> +		return false;
> +
> +	if (on)
> +		test_ctrl_val |= MSR_TEST_CTRL_SPLIT_LOCK_DETECT;
> +	else
> +		test_ctrl_val &= ~MSR_TEST_CTRL_SPLIT_LOCK_DETECT;
> +
> +	return !wrmsrl_safe(MSR_TEST_CTRL, test_ctrl_val);
> +}
> +
> +static void split_lock_init(void)
> +{
> +	if (sld_state == sld_off)
> +		return;
> +
> +	if (__sld_msr_set(true))
> +		return;
> +
> +	/*
> +	 * If this is anything other than the boot-cpu, you've done
> +	 * funny things and you get to keep whatever pieces.
> +	 */
> +	pr_warn("MSR fail -- disabled\n");
> +	__sld_msr_set(sld_off);

This one is pretty pointless. If the rdmsrl or the wrmsrl failed, then
the next attempt is going to fail too. Aside of that sld_off would be not
really the right argument value here. I just zap that line.

Thanks,

        tglx