arch/x86,cpu/x86,lib/thread: Remove usage of cpu_info from lib/thread

We only ever start and execute threads on the BSP. By explicitly
checking to see if the CPU is the BSP we can remove the dependency on
cpu_info. With this change we can in theory enable threads in all
stages.

BUG=b:194391185, b:179699789
TEST=Boot guybrush to OS and verify coop multithreading still works

Suggested-by: Julius Werner <jwerner@chromium.org>
Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: Iea4622d52c36d529e100b7ea55f32c334acfdf3e
Reviewed-on: https://review.coreboot.org/c/coreboot/+/58199
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

6 files changed, 15 insertions, 23 deletions

diff --git a/src/arch/x86/include/arch/cpu.h b/src/arch/x86/include/arch/cpu.h
index 8e96fae2c2..9a3b63d6b3 100644
--- a/src/arch/x86/include/arch/cpu.h
+++ b/src/arch/x86/include/arch/cpu.h
@@ -231,9 +231,6 @@ struct thread;
 struct cpu_info {
 	struct device *cpu;
 	size_t index;
-#if CONFIG(COOP_MULTITASKING)
-	struct thread *thread;
-#endif
 };
 
 /*
diff --git a/src/cpu/x86/cpu_info.S.inc b/src/cpu/x86/cpu_info.S.inc
index dffd1bc346..fc3e26d178 100644
--- a/src/cpu/x86/cpu_info.S.inc
+++ b/src/cpu/x86/cpu_info.S.inc
@@ -2,9 +2,6 @@
 
 /* Push struct cpu_info */
 .macro push_cpu_info index=$0
-#if CONFIG(COOP_MULTITASKING)
-	push	$0	/* *thread */
-#endif
 	push	\index	/* index */
 	push	$0	/* *cpu */
 .endm
diff --git a/src/cpu/x86/lapic/lapic_cpu_init.c b/src/cpu/x86/lapic/lapic_cpu_init.c
index bc0f44fd90..c35888a7fd 100644
--- a/src/cpu/x86/lapic/lapic_cpu_init.c
+++ b/src/cpu/x86/lapic/lapic_cpu_init.c
@@ -253,7 +253,6 @@ static int start_cpu(struct device *cpu)
 	info->index = index;
 	info->cpu   = cpu;
 	cpu_add_map_entry(info->index);
-	thread_init_cpu_info_non_bsp(info);
 
 	/* Advertise the new stack and index to start_cpu */
 	secondary_stack = stack_top;
diff --git a/src/cpu/x86/mp_init.c b/src/cpu/x86/mp_init.c
index 123b2b5eb5..497ed3cfc5 100644
--- a/src/cpu/x86/mp_init.c
+++ b/src/cpu/x86/mp_init.c
@@ -193,7 +193,6 @@ static void asmlinkage ap_init(unsigned int cpu)
 	info->cpu = cpus_dev[cpu];
 
 	cpu_add_map_entry(info->index);
-	thread_init_cpu_info_non_bsp(info);
 
 	/* Fix up APIC id with reality. */
 	info->cpu->path.apic.apic_id = lapicid();
diff --git a/src/include/thread.h b/src/include/thread.h
index cb085b5509..62c6283acf 100644
--- a/src/include/thread.h
+++ b/src/include/thread.h
@@ -73,11 +73,6 @@ void thread_coop_disable(void);
 void thread_mutex_lock(struct thread_mutex *mutex);
 void thread_mutex_unlock(struct thread_mutex *mutex);
 
-static inline void thread_init_cpu_info_non_bsp(struct cpu_info *ci)
-{
-	ci->thread = NULL;
-}
-
 /* Architecture specific thread functions. */
 asmlinkage void switch_to_thread(uintptr_t new_stack, uintptr_t *saved_stack);
 /* Set up the stack frame for a new thread so that a switch_to_thread() call
@@ -96,8 +91,6 @@ static inline int thread_yield_microseconds(unsigned int microsecs)
 }
 static inline void thread_coop_enable(void) {}
 static inline void thread_coop_disable(void) {}
-struct cpu_info;
-static inline void thread_init_cpu_info_non_bsp(struct cpu_info *ci) { }
 
 static inline void thread_mutex_lock(struct thread_mutex *mutex) {}
 
diff --git a/src/lib/thread.c b/src/lib/thread.c
index 9008147eae..da6189d6f1 100644
--- a/src/lib/thread.c
+++ b/src/lib/thread.c
@@ -4,10 +4,10 @@
 #include <stddef.h>
 #include <stdint.h>
 #include <stdlib.h>
-#include <arch/cpu.h>
 #include <bootstate.h>
 #include <commonlib/bsd/compiler.h>
 #include <console/console.h>
+#include <smp/node.h>
 #include <thread.h>
 #include <timer.h>
 
@@ -27,17 +27,25 @@ static struct thread all_threads[TOTAL_NUM_THREADS];
 static struct thread *runnable_threads;
 static struct thread *free_threads;
 
+static struct thread *active_thread;
+
 static inline int thread_can_yield(const struct thread *t)
 {
 	return (t != NULL && t->can_yield > 0);
 }
 
+static inline void set_current_thread(struct thread *t)
+{
+	assert(boot_cpu());
+	active_thread = t;
+}
+
 static inline struct thread *current_thread(void)
 {
-	if (!initialized)
+	if (!initialized || !boot_cpu())
 		return NULL;
 
-	return cpu_info()->thread;
+	return active_thread;
 }
 
 static inline int thread_list_empty(struct thread **list)
@@ -108,7 +116,6 @@ __noreturn static enum cb_err idle_thread(void *unused)
 static void schedule(struct thread *t)
 {
 	struct thread *current = current_thread();
-	struct cpu_info *ci = cpu_info();
 
 	/* If t is NULL need to find new runnable thread. */
 	if (t == NULL) {
@@ -123,7 +130,7 @@ static void schedule(struct thread *t)
 	if (t->handle)
 		t->handle->state = THREAD_STARTED;
 
-	ci->thread = t;
+	set_current_thread(t);
 
 	switch_to_thread(t->stack_current, &current->stack_current);
 }
@@ -239,14 +246,14 @@ static void threads_initialize(void)
 	int i;
 	struct thread *t;
 	u8 *stack_top;
-	struct cpu_info *ci;
 
 	if (initialized)
 		return;
 
 	t = &all_threads[0];
-	ci = cpu_info();
-	ci->thread = t;
+
+	set_current_thread(t);
+
 	t->stack_orig = (uintptr_t)NULL; /* We never free the main thread */
 	t->id = 0;
 	t->can_yield = 1;