From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752206AbaBGAwm (ORCPT ); Thu, 6 Feb 2014 19:52:42 -0500 Received: from pinero.vault24.org ([69.164.212.126]:38899 "EHLO pinero.vault24.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751531AbaBGAwj (ORCPT ); Thu, 6 Feb 2014 19:52:39 -0500 X-Greylist: delayed 392 seconds by postgrey-1.27 at vger.kernel.org; Thu, 06 Feb 2014 19:52:39 EST Date: Thu, 6 Feb 2014 19:45:34 -0500 From: Jon To: linux-kernel@vger.kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org Subject: [PROBLEM] x86: result of verify_local_APIC() is ignored Message-ID: <20140207004534.GI3232@feynman.vault24.org> Mail-Followup-To: linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In arch/x86/kernel/apic/apic.c there is a function called verify_local_APIC() that does some APIC checks. The part where it writes to the APIC ID register can cause CPU #15 to not come online under VMware ESXi on 32-bit kernels if the virtual hardware version is 8. I noticed that Ingo actually removed this exact chunk of code from arch/i386/kernel/apic.c in 2.6.4, but since it was left in the x86_64 copy it came back when the two were merged. http://permalink.gmane.org/gmane.linux.kernel.commits.head/27538 The Intel architecture manuals seem to agree and notes that the recent Intel CPUs do not allow writing to the register which means that machines are actually failing this check... which doesn't matter becuase none of the callers are checking the return value of this function anyway. -- Jon X(7): A program for managing terminal windows. See also screen(1).