On Fri, 31 Jul 2015, Shaohua Li wrote:
> @@ -336,6 +336,22 @@ static void __setup_APIC_LVTT(unsigned int clocks, int oneshot, int irqen)
> apic_write(APIC_LVTT, lvtt_value);
>
> if (lvtt_value & APIC_LVT_TIMER_TSCDEADLINE) {
> + u64 msr;
> +
> + /*
> + * See Intel SDM: TSC-Deadline Mode chapter. In xAPIC mode,
> + * writing APIC LVTT and TSC_DEADLINE MSR isn't serialized.
> + * This uses the algorithm described in Intel SDM to serialize
> + * the two writes
> + * */
> + while (1) {
> + wrmsrl(MSR_IA32_TSC_DEADLINE, -1L);
> + rdmsrl(MSR_IA32_TSC_DEADLINE, msr);
> + if (msr)
> + break;
> + }
> + wrmsrl(MSR_IA32_TSC_DEADLINE, 0);
I think this is exceptionally silly. A proper fence after the
apic_write() should have the same effect.
Thanks,
tglx
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