Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751539AbdIKPEr (ORCPT ); Mon, 11 Sep 2017 11:04:47 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:31977 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751509AbdIKPEq (ORCPT ); Mon, 11 Sep 2017 11:04:46 -0400 From: Boris Ostrovsky To: hpa@zytor.com, mingo@redhat.com, tglx@linutronix.de Cc: baolu.lu@linux.intel.com, linux-kernel@vger.kernel.org, x86@kernel.org, Boris Ostrovsky Subject: [PATCH] x86/timers: Move simple_udelay_calibration() past kvmclock_init() Date: Mon, 11 Sep 2017 11:04:19 -0400 Message-Id: <20170911150419.14035-1-boris.ostrovsky@oracle.com> X-Mailer: git-send-email 2.11.0 X-Source-IP: aserv0022.oracle.com [141.146.126.234] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1328 Lines: 43 simple_udelay_calibration() relies on x86_platform's calibration ops. For KVM these ops are set late in setup_arch() and so simple_udelay_calibration() ends up using native version. Besides being possibly incorrect, this significantly increases kernel boot time. For example, on my laptop executing start_kernel() by a guest takes ~10 times more than when KVM's ops are used. Signed-off-by: Boris Ostrovsky --- Alternatively, we could start calling simple_udelay_calibration() only on bare metal: My understanding is that the only reason it exists is to help with USB3 earlyprink driver, which I don't think is useful to guests anyway. arch/x86/kernel/setup.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index f81823695014..749439fba076 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -1039,8 +1039,6 @@ void __init setup_arch(char **cmdline_p) */ init_hypervisor_platform(); - simple_udelay_calibration(); - x86_init.resources.probe_roms(); /* after parse_early_param, so could debug it */ @@ -1221,6 +1219,8 @@ void __init setup_arch(char **cmdline_p) kvmclock_init(); #endif + simple_udelay_calibration(); + x86_init.paging.pagetable_init(); kasan_init(); -- 2.11.0