From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757339AbXEIUEF (ORCPT ); Wed, 9 May 2007 16:04:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754240AbXEIUDz (ORCPT ); Wed, 9 May 2007 16:03:55 -0400 Received: from mx1.redhat.com ([66.187.233.31]:46702 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751722AbXEIUDz (ORCPT ); Wed, 9 May 2007 16:03:55 -0400 Date: Wed, 9 May 2007 12:56:16 -0700 From: Pete Zaitcev To: Cc: zaitcev@redhat.com, linux-kernel@vger.kernel.org, Subject: Andi, you broke my laptop :-) Message-Id: <20070509125616.cde56b8e.zaitcev@redhat.com> Organization: Red Hat, Inc. X-Mailer: Sylpheed 2.3.1 (GTK+ 2.10.11; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi, Andi: The attached patch (actually, git show output) makes my Dell 1501 to hang on boot. Sorry, I have no clue why... The culprit is found with git bisect. But yes, it's an AMD MK-36. I use an x86_64 kernel. It is 100% reproducible. Cheers, -- Pete commit c5bcb5635a03da3158f121ae20ccbbf72b4fc62a Author: Andi Kleen Date: Wed May 2 19:27:21 2007 +0200 [PATCH] x86: Use RDTSCP for synchronous get_cycles if possible RDTSCP is already synchronous and doesn't need an explicit CPUID. This is a little faster and more importantly avoids VMEXITs on Hypervisors. Original patch from Joerg Roedel, but reworked by AK Also includes miscompilation fix by Eric Biederman Cc: "Joerg Roedel" Signed-off-by: Andi Kleen diff --git a/include/asm-i386/tsc.h b/include/asm-i386/tsc.h index 0181f9d..3f3c1fa 100644 --- a/include/asm-i386/tsc.h +++ b/include/asm-i386/tsc.h @@ -38,6 +38,15 @@ static __always_inline cycles_t get_cycles_sync(void) unsigned eax; /* + * Use RDTSCP if possible; it is guaranteed to be synchronous + * and doesn't cause a VMEXIT on Hypervisors + */ + alternative_io(ASM_NOP3, ".byte 0x0f,0x01,0xf9", X86_FEATURE_RDTSCP, + "=A" (ret), "0" (0ULL) : "ecx", "memory"); + if (ret) + return ret; + + /* * Don't do an additional sync on CPUs where we know * RDTSC is already synchronous: */