From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933467AbbCRUqF (ORCPT ); Wed, 18 Mar 2015 16:46:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33883 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933376AbbCRUqD (ORCPT ); Wed, 18 Mar 2015 16:46:03 -0400 From: Bandan Das To: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" Cc: x86@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] x86/apic: remove read/write test in verify_local_apic() User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.4 (gnu/linux) Date: Wed, 18 Mar 2015 16:45:54 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Most newer processors have the APIC_ID read-only and this test probably fails on most boxes anyway. Fix typos. Signed-off-by: Bandan Das --- Honestly, I don't think this function is really needed. It's called for both UP/MP but the return value isn't used by any of them. Maybe, we should just remove it ? arch/x86/kernel/apic/apic.c | 18 +++++++----------- 1 file changed, 7 insertions(+), 11 deletions(-) diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index ad3639a..d54601e 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -1105,13 +1105,13 @@ int __init verify_local_APIC(void) /* * The two version reads above should print the same * numbers. If the second one is different, then we - * poke at a non-APIC. + * are poking at a non-APIC region. */ if (reg1 != reg0) return 0; /* - * Check if the version looks reasonably. + * Check if the version looks reasonable. */ reg1 = GET_APIC_VERSION(reg0); if (reg1 == 0x00 || reg1 == 0xff) @@ -1121,21 +1121,17 @@ int __init verify_local_APIC(void) return 0; /* - * The ID register is read/write in a real APIC. + * Just print the APIC ID + * Writing to it is not a reliable test - older processors + * support it, while newer processors don't */ reg0 = apic_read(APIC_ID); - apic_printk(APIC_DEBUG, "Getting ID: %x\n", reg0); - apic_write(APIC_ID, reg0 ^ apic->apic_id_mask); - reg1 = apic_read(APIC_ID); - apic_printk(APIC_DEBUG, "Getting ID: %x\n", reg1); - apic_write(APIC_ID, reg0); - if (reg1 != (reg0 ^ apic->apic_id_mask)) - return 0; + apic_printk(APIC_DEBUG, "Getting Local APIC ID: %x\n", reg0); /* * The next two are just to see if we have sane values. * They're only really relevant if we're in Virtual Wire - * compatibility mode, but most boxes are anymore. + * compatibility mode, but most boxes aren't anymore. */ reg0 = apic_read(APIC_LVT0); apic_printk(APIC_DEBUG, "Getting LVT0: %x\n", reg0); -- 2.1.0