Date: Wed, 14 Sep 2016 22:25:36 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: Konstantin Belousov <kostikbel@gmail.com>, Slawa Olhovchenkov <slw@zxy.spb.ru> Cc: stable@FreeBSD.org Subject: Re: X2APIC support Message-ID: <791a83d5-3303-038f-7912-9a2671eba485@FreeBSD.org> In-Reply-To: <20160914160802.GH38409@kib.kiev.ua> References: <20160913142118.GA34394@zxy.spb.ru> <37f5cebc-3fa1-9e95-5123-f3d8daa3130a@FreeBSD.org> <20160913152240.GE38409@kib.kiev.ua> <cb35f671-95e7-820f-6a78-ee60612cc1ad@FreeBSD.org> <20160914113634.GF38409@kib.kiev.ua> <763df55a-4b69-9f7a-1042-0f631a729881@FreeBSD.org> <20160914123313.GC2840@zxy.spb.ru> <966c58d6-db64-2879-6709-0aa596bec24b@FreeBSD.org> <20160914124950.GE2840@zxy.spb.ru> <50cf91d9-072d-76fe-768c-8a6a9515bd93@FreeBSD.org> <20160914160802.GH38409@kib.kiev.ua>
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On 14/09/2016 19:08, Konstantin Belousov wrote: > Well, the following might work, but I have no good idea what to do > when BIOS does handoff with x2APIC enabled and directs us to not > enable it. Switching to xAPIC mode is not an option, I suspect. The specification describes a way to transition from x2APIC to xAPIC mode, but it's not trivial, because it requires checking all CPU IDs and disabling CPUs with too high ones. Personally, I am not comfortable with your patch. First, it seems that the patch does not cover hw.x2apic_enable=0. And I don't like that we leave x2APIC mode enabled even when we otherwise would not enable it just because BIOS. All in all, if we can't go x2APIC -> xAPIC, then I would prefer a meaningful panic over a "compromise". Just my opinion. The topic probably warrants a wider discussion and a proper review. Slawa, thank you for your persistence and testing. -- Andriy Gapon
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