From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: KVM crash on unusual PM->RM transition Date: Mon, 13 Apr 2009 16:42:25 -0700 Message-ID: <49E3CDE1.8010001@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit To: kvm@vger.kernel.org Return-path: Received: from terminus.zytor.com ([198.137.202.10]:51134 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752387AbZDMXm0 (ORCPT ); Mon, 13 Apr 2009 19:42:26 -0400 Sender: kvm-owner@vger.kernel.org List-ID: The current test branch of Syslinux does PM->RM transition via a stub which can be located in high memory. This is correct and valid (x86 CPUs rely on this to boot): after clearing CR0.PE, CS.base retains its previous value until CS is reloaded by a far JMP (which in this case is the very next instruction). Unfortunately, at least on a stock Fedora 10 system, KVM doesn't agree: : anacreon 67 ; qemu-kvm -boot d -cdrom image.iso unhandled vm exit: 0x80000021 vcpu_id 0 rax 0000000000000012 rbx 0000000007ade342 rcx 0000000000000000 rdx 0000000007ade388 rsi 0000000000000000 rdi 0000000000800000 rsp 0000000007ade448 rbp 0000000000007b94 r8 0000000000000000 r9 0000000000000000 r10 0000000000000000 r11 0000000000000000 r12 0000000000000000 r13 0000000000000000 r14 0000000000000000 r15 0000000000000000 rip 0000000000000008 rflags 00023006 cs de36 (07ade36e/0000ffff p 1 dpl 3 db 0 s 1 type 3 l 0 g 0 avl 0) ds 0000 (00000000/0000ffff p 1 dpl 3 db 0 s 1 type 3 l 0 g 0 avl 0) es 0000 (00000000/0000ffff p 1 dpl 3 db 0 s 1 type 3 l 0 g 0 avl 0) ss 0000 (00000000/0000ffff p 1 dpl 3 db 0 s 1 type 3 l 0 g 0 avl 0) fs 0000 (00000000/0000ffff p 1 dpl 3 db 0 s 1 type 3 l 0 g 0 avl 0) gs 0000 (00000000/0000ffff p 1 dpl 3 db 0 s 1 type 3 l 0 g 0 avl 0) tr 0030 (fffbd000/00002088 p 1 dpl 0 db 0 s 0 type b l 0 g 0 avl 0) ldt 0000 (00000000/ffffffff p 0 dpl 0 db 0 s 0 type 0 l 0 g 0 avl 0) gdt 7ade388/3f idt 0/ffff cr0 12 cr2 0 cr3 0 cr4 0 cr8 0 efer 0 Abort Kernel 2.6.27.21-170.2.56.fc10.x86_64, kvm-74-10.fc10.x86_64. -hpa