On Sun, Sep 04, 2016 at 06:49:43PM +0300, Andriy Gapon wrote: > On 04/09/2016 18:14, Konstantin Belousov wrote: > > On Sun, Sep 04, 2016 at 11:19:16AM +0300, Andriy Gapon wrote: > >> Kostik, I see one strange thing which is common to both successful and > >> unsuccessful configurations. All "SMP: Added CPU..." lines have "AP" in > >> them. > >> It seems like the platform does not tell explicitly tell which CPU is the > >> BSP, > >> see cpu_add() function. This can break quite a few assumption. And I am > >> not > >> even sure how the successful scenario works. > >> Ah... I see that there is a backup code in cpu_mp_start() where > >> boot_cpu_id is > >> set based on the current CPU's Local APIC ID. I suspect then that this > >> information is incorrect in the failing case. > >> > > Well, there is no easy way to read the LAPIC Id of BSP before LAPICs > > are initialized. BIOS might reprogram LAPIC Ids, so reading from > > CPUID[1].EBX[31:24] might return incorrect data. Even more incorrect > > it might be in the x2APIC state, since 8 bits are not enough for 32bit > > x2APIC Id. > > Hmm, I am not sure how what you are saying here is relevant to the problem. > I believe that cpu_mp_start() is executed (on the BSP) after the BSP's LAPIC > is > initialized. So, the code should just work. The order is madt_probe()->madt_probe_cpus()->madt_setup_local().
madt_probe() and madt_probe_cpus() are called from apic_init9) at SI_SUB_TUNABLEs, and madt_probe_cpus()->madt_add_cpu()->lapic_create()-> cpu_add() is how the SMP: ... lines are printed. The madt_setup_local() code is called from apic_setup_local() at SI_SUB_CPU, this is where APIC window is mapped or x2APIC mode is enabled by the call to native_lapic_init(). You cannot get BSP LAPIC Id earlier than native_lapic_init() was executed. mp_start()->cpu_mp_start() is called right after the madt_setup_local(). > > My theory was that the BSP's LAPIC ID was incorrectly programmed by BIOS > (firmware). This is possible, of course. But it would not affect "SMP: Added CPU ..." lines. _______________________________________________ freebsd-stable@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "freebsd-stable-unsubscr...@freebsd.org"
