Change in coreboot[master]: cpu/x86/mp_init.c: Add wait_finished_mp_run_on_all_cpus

[Arthur Heymans (Code Review)]

Attention is currently required from: Subrata Banik, Kane Chen, Tim Wawrzynczak, Arthur Heymans.
Arthur Heymans has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/63566 )

Change subject: cpu/x86/mp_init.c: Add wait_finished_mp_run_on_all_cpus
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Patch Set 4:

(2 comments)

File src/cpu/x86/mp_init.c:

https://review.coreboot.org/c/coreboot/+/63566/comment/29afc42b_029e8272 
PS4, Line 882: 
             : 
             : static void store_ap_busy(bool *ap_busy_flag, bool val)
             : {
             : 	asm volatile ("mov	%1, %0\n"
             : 		: "=m" (*ap_busy_flag)
             : 		: "r" (val)
             : 		: "memory"
             : 	);
             : }
             : 
             : static bool read_ap_busy(bool *ap_busy_flag)
             : {
             :     bool ret;
             : 	asm volatile ("mov	%1, %0\n"
             : 		: "=r" (ret)
             : 		: "m" (*ap_busy_flag)
             : 		: "memory"
             : 	);
             : 	return ret;
             : }
Since bool == int compiler-wise I think the atomic_t type & ops will work fine.

https://review.coreboot.org/c/coreboot/+/63566/comment/8d2a6577_a1670091 
PS4, Line 994: if (lcb.logical_cpu_number && (cur_cpu !=
             : 				lcb.logical_cpu_number))
             : 			continue;
Here you'll skip clearing the busy bit. I think it will be easier if you set & clear the busy bit from the APs instead of from the BSP call.