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: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20231002115903.433704135@linutronix.de

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 1ff38f9fdb8a9d28b30f0e02d9d55dba47c04879..1c2710b7db6d7402bf20a7a288a7872a482a43a1 100644 (file)
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -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