lib/thread: Switch to using CPU_INFO_V2

CPU_INFO_V2 changes the behavior of cpu_info(). There is now only 1
cpu_info struct per cpu. This means that we no longer need to allocate
it at the top of each threads stack.

We can now in theory remove the CONFIG_STACK_SIZE alignment on the
thread stack sizes. We can also in theory use threads in SMM if you are
feeling venturesome.

BUG=b:194391185, b:179699789
TEST=Perform reboot stress test on guybrush with COOP_MULTITASKING
enabled.

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: I5e04d254a00db43714ec60ebed7c4aa90e23190a
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57628
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Eric Peers <epeers@google.com>
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>

2 files changed, 6 insertions, 23 deletions

diff --git a/src/Kconfig b/src/Kconfig
index 09bc22dad16c..ea05215bdd49 100644
--- a/src/Kconfig
+++ b/src/Kconfig
@@ -677,7 +677,7 @@ config TIMER_QUEUE
 
 config COOP_MULTITASKING
 	def_bool n
-	depends on TIMER_QUEUE && ARCH_X86
+	depends on TIMER_QUEUE && ARCH_X86 && CPU_INFO_V2
 	help
 	  Cooperative multitasking allows callbacks to be multiplexed on the
 	  main thread of ramstage. With this enabled it allows for multiple
diff --git a/src/lib/thread.c b/src/lib/thread.c
index 2ff09a50d5d3..ac8460c964df 100644
--- a/src/lib/thread.c
+++ b/src/lib/thread.c
@@ -36,28 +36,17 @@ static struct thread all_threads[TOTAL_NUM_THREADS];
 static struct thread *runnable_threads;
 static struct thread *free_threads;
 
-static inline struct cpu_info *thread_cpu_info(const struct thread *t)
-{
-	return (void *)(t->stack_orig);
-}
-
 static inline int thread_can_yield(const struct thread *t)
 {
 	return (t != NULL && t->can_yield > 0);
 }
 
-/* Assumes current CPU info can switch. */
-static inline struct thread *cpu_info_to_thread(const struct cpu_info *ci)
-{
-	return ci->thread;
-}
-
 static inline struct thread *current_thread(void)
 {
 	if (!initialized)
 		return NULL;
 
-	return cpu_info_to_thread(cpu_info());
+	return cpu_info()->thread;
 }
 
 static inline int thread_list_empty(struct thread **list)
@@ -94,21 +83,12 @@ static inline struct thread *pop_runnable(void)
 static inline struct thread *get_free_thread(void)
 {
 	struct thread *t;
-	struct cpu_info *ci;
-	struct cpu_info *new_ci;
 
 	if (thread_list_empty(&free_threads))
 		return NULL;
 
 	t = pop_thread(&free_threads);
 
-	ci = cpu_info();
-
-	/* Initialize the cpu_info structure on the new stack. */
-	new_ci = thread_cpu_info(t);
-	*new_ci = *ci;
-	new_ci->thread = t;
-
 	/* Reset the current stack value to the original. */
 	t->stack_current = t->stack_orig;
 
@@ -134,6 +114,7 @@ __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) {
@@ -148,6 +129,8 @@ static void schedule(struct thread *t)
 	if (t->handle)
 		t->handle->state = THREAD_STARTED;
 
+	ci->thread = t;
+
 	switch_to_thread(t->stack_current, &current->stack_current);
 }
 
@@ -279,7 +262,7 @@ static void threads_initialize(void)
 	t->id = 0;
 	t->can_yield = 1;
 
-	stack_top = &thread_stacks[CONFIG_STACK_SIZE] - sizeof(struct cpu_info);
+	stack_top = &thread_stacks[CONFIG_STACK_SIZE];
 	for (i = 1; i < TOTAL_NUM_THREADS; i++) {
 		t = &all_threads[i];
 		t->stack_orig = (uintptr_t)stack_top;