Commit 0bf87165 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Borislav Petkov (AMD)
Browse files

x86/microcode: Replace the all-in-one rendevous handler 



with a new handler which just separates the control flow of primary and
secondary CPUs.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20231002115903.433704135@linutronix.de
parent 6067788f

arch/x86/kernel/cpu/microcode/core.c

+9 −42
Original line number Diff line number Diff line
@@ -268,7 +268,7 @@ struct microcode_ctrl { 
};



static DEFINE_PER_CPU(struct microcode_ctrl, ucode_ctrl);

static atomic_t late_cpus_in, late_cpus_out;

static atomic_t late_cpus_in;



static bool wait_for_cpus(atomic_t *cnt)

{
@@ -304,7 +304,7 @@ static bool wait_for_ctrl(void) 
	return false;

}



static __maybe_unused void load_secondary(unsigned int cpu)

static void load_secondary(unsigned int cpu)

{

	unsigned int ctrl_cpu = this_cpu_read(ucode_ctrl.ctrl_cpu);

	enum ucode_state ret;
@@ -339,7 +339,7 @@ static __maybe_unused void load_secondary(unsigned int cpu) 
	this_cpu_write(ucode_ctrl.ctrl, SCTRL_DONE);

}



static __maybe_unused void load_primary(unsigned int cpu)

static void load_primary(unsigned int cpu)

{

	struct cpumask *secondaries = topology_sibling_cpumask(cpu);

	enum sibling_ctrl ctrl;
@@ -376,46 +376,14 @@ static __maybe_unused void load_primary(unsigned int cpu) 


static int load_cpus_stopped(void *unused)

{

	int cpu = smp_processor_id();

	enum ucode_state ret;



	/*

	 * Wait for all CPUs to arrive. A load will not be attempted unless all

	 * CPUs show up.

	 * */

	if (!wait_for_cpus(&late_cpus_in)) {

		this_cpu_write(ucode_ctrl.result, UCODE_TIMEOUT);

		return 0;

	}



	/*

	 * On an SMT system, it suffices to load the microcode on one sibling of

	 * the core because the microcode engine is shared between the threads.

	 * Synchronization still needs to take place so that no concurrent

	 * loading attempts happen on multiple threads of an SMT core. See

	 * below.

	 */

	if (cpumask_first(topology_sibling_cpumask(cpu)) != cpu)

		goto wait_for_siblings;

	unsigned int cpu = smp_processor_id();



	ret = microcode_ops->apply_microcode(cpu);

	this_cpu_write(ucode_ctrl.result, ret);



wait_for_siblings:

	if (!wait_for_cpus(&late_cpus_out))

		panic("Timeout during microcode update!\n");



	/*

	 * At least one thread has completed update on each core.

	 * For others, simply call the update to make sure the

	 * per-cpu cpuinfo can be updated with right microcode

	 * revision.

	 */

	if (cpumask_first(topology_sibling_cpumask(cpu)) == cpu)

		return 0;

	if (this_cpu_read(ucode_ctrl.ctrl_cpu) == cpu)

		load_primary(cpu);

	else

		load_secondary(cpu);



	ret = microcode_ops->apply_microcode(cpu);

	this_cpu_write(ucode_ctrl.result, ret);

	/* No point to wait here. The CPUs will all wait in stop_machine(). */

	return 0;

}
@@ -429,7 +397,6 @@ static int load_late_stop_cpus(void) 
	pr_err("You should switch to early loading, if possible.\n");



	atomic_set(&late_cpus_in, num_online_cpus());

	atomic_set(&late_cpus_out, num_online_cpus());



	/*

	 * Take a snapshot before the microcode update in order to compare and