Date: Sun, 4 Sep 2016 18:49:43 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: Slawa Olhovchenkov <slw@zxy.spb.ru>, stable@FreeBSD.org Subject: Re: X2APIC support Message-ID: <f727b18d-6061-fbaf-6afc-1ae66f8cce16@FreeBSD.org> In-Reply-To: <20160904151415.GE83214@kib.kiev.ua> References: <20151212130615.GE70867@zxy.spb.ru> <20151212133513.GL82577@kib.kiev.ua> <20160901112724.GX88122@zxy.spb.ru> <20160901114500.GJ83214@kib.kiev.ua> <20160901121300.GZ88122@zxy.spb.ru> <4ba05c00-f737-f562-553d-a7fa59145768@FreeBSD.org> <20160904151415.GE83214@kib.kiev.ua>
next in thread | previous in thread | raw e-mail | index | archive | help
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. My theory was that the BSP's LAPIC ID was incorrectly programmed by BIOS (firmware). -- Andriy Gapon
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?f727b18d-6061-fbaf-6afc-1ae66f8cce16>