Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932164AbXAQKDv (ORCPT ); Wed, 17 Jan 2007 05:03:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932189AbXAQKDv (ORCPT ); Wed, 17 Jan 2007 05:03:51 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:46564 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932164AbXAQKDu (ORCPT ); Wed, 17 Jan 2007 05:03:50 -0500 Date: Wed, 17 Jan 2007 11:02:10 +0100 From: Ingo Molnar To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Avi Kivity Subject: Re: [patch] KVM: do VMXOFF upon reboot Message-ID: <20070117100210.GA13080@elte.hu> References: <20070117091319.GA30036@elte.hu> <20070117095141.GA11341@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070117095141.GA11341@elte.hu> User-Agent: Mutt/1.4.2.2i X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -3.3 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-3.3 required=5.9 tests=ALL_TRUSTED autolearn=no SpamAssassin version=3.0.3 -3.3 ALL_TRUSTED Did not pass through any untrusted hosts Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2948 Lines: 94 * Ingo Molnar wrote: > So i think we should do the patch below - this makes reboot work even > in atomic contexts. [...] hm, this causes problems if KVM is not active on a VT-capable CPU: even on CPUs with VT supported, if a VT context is not actually activated, a vmxoff causes an invalid opcode exception. So the updated patch below uses a slightly more sophisticated approach to avoid that problem. Ingo --------------------> Subject: [patch] kvm: do VMXOFF upon reboot From: Ingo Molnar my laptop's BIOS apparently gets confused if the kernel tries to reboot without first turning VT context off, which results in a hung (emergency-)reboot. So make sure this happens, right before we reboot. ( NOTE: this is a dual-core system, but only the core where the BIOS executes seems to be affected - the other core can have an active VT context just fine - so we dont have to risk reboot robustness by doing a CPU cross-call in the emergency reboot handler. ) Signed-off-by: Ingo Molnar --- arch/i386/kernel/reboot.c | 16 ++++++++++++++++ arch/x86_64/kernel/reboot.c | 15 +++++++++++++++ 2 files changed, 31 insertions(+) Index: linux/arch/i386/kernel/reboot.c =================================================================== --- linux.orig/arch/i386/kernel/reboot.c +++ linux/arch/i386/kernel/reboot.c @@ -318,6 +318,22 @@ void machine_shutdown(void) void machine_emergency_restart(void) { + unsigned long ecx = cpuid_ecx(1); + + /* + * Disable any possibly active VT context (if VT supported): + */ + if (test_bit(5, &ecx)) { /* has VT support */ + asm volatile ( + "1: .byte 0x0f, 0x01, 0xc4 \n" /* vmxoff */ + "2: \n" + ".section __ex_table,\"a\" \n" + " .align 4 \n" + " .long 1b,2b \n" + ".previous \n" + ); + } + if (!reboot_thru_bios) { if (efi_enabled) { efi.reset_system(EFI_RESET_COLD, EFI_SUCCESS, 0, NULL); Index: linux/arch/x86_64/kernel/reboot.c =================================================================== --- linux.orig/arch/x86_64/kernel/reboot.c +++ linux/arch/x86_64/kernel/reboot.c @@ -114,8 +114,23 @@ void machine_shutdown(void) void machine_emergency_restart(void) { + unsigned long ecx = cpuid_ecx(1); int i; + /* + * Disable any possibly active VT context (if VT supported): + */ + if (test_bit(5, &ecx)) { /* has VT support */ + asm volatile ( + "1: .byte 0x0f, 0x01, 0xc4 \n" /* vmxoff */ + "2: \n" + ".section __ex_table,\"a\" \n" + " .align 8 \n" + " .quad 1b,2b \n" + ".previous \n" + ); + } + /* Tell the BIOS if we want cold or warm reboot */ *((unsigned short *)__va(0x472)) = reboot_mode; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/