From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: Problem with KVM guest switching to x86 long mode Date: Thu, 08 Apr 2010 21:36:03 +0300 Message-ID: <4BBE2213.6020802@redhat.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: KVM General To: Pekka Enberg Return-path: Received: from mx1.redhat.com ([209.132.183.28]:25239 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933009Ab0DHSgP (ORCPT ); Thu, 8 Apr 2010 14:36:15 -0400 In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On 04/08/2010 09:26 PM, Pekka Enberg wrote: > Hi! > > I am working on a light-weight KVM userspace launcher for Linux and am > bit stuck with a guest Linux kernel restarting when it tries to enter > long mode. > > The register dump looks like this: > > penberg@tiger:~/vm$ ./kvm bzImage > KVM exit reason: 8 ("KVM_EXIT_SHUTDOWN") > Registers: > rip: 00000000001000ed rsp: 00000000005d54b8 flags: 0000000000010046 > rax: 0000000080000001 rbx: 0000000001f2c000 rcx: 00000000c0000080 > rdx: 0000000000000000 rsi: 0000000000013670 rdi: 0000000002408000 > rbp: 0000000000100000 r8: 0000000000000000 r9: 0000000000000000 > r10: 0000000000000000 r11: 0000000000000000 r12: 0000000000000000 > r13: 0000000000000000 r14: 0000000000000000 r15: 0000000000000000 > cr0: 0000000080000011 cr2: 00000000001000ed cr3: 0000000002402000 > cr4: 0000000000000020 cr8: 0000000000000000 > Segment registers: > register selector base limit type p dpl db s l g avl > cs 0010 0000000000000000 ffffffff 0b 1 0 1 1 0 1 0 > ss 0018 0000000000000000 ffffffff 03 1 0 1 1 0 1 0 > ds 0018 0000000000000000 ffffffff 03 1 0 1 1 0 1 0 > es 0018 0000000000000000 ffffffff 03 1 0 1 1 0 1 0 > fs 0018 0000000000000000 ffffffff 03 1 0 1 1 0 1 0 > gs 0018 0000000000000000 ffffffff 03 1 0 1 1 0 1 0 > tr 0020 0000000000001000 00000067 0b 1 0 0 0 0 0 0 > ldt 0000 0000000000000000 ffffffff 00 0 0 0 0 0 0 0 > These all look reasonable. Please add a gdtr dump and an idtr dump. > 2b:* cb lret<-- trapping instruction > Post the two u32s at ss:rsp -> ss:rsp+8. That will tell us where the guest is trying to return. Actually, from the dump: 1a: 6a 10 pushq $0x10 1c: 8d 85 00 02 00 00 lea 0x200(%rbp),%eax 22: 50 push %rax it looks like you're returning to segment 0x10, this should be the word at ss:rsp+4. So if you dump the 2 u32s at gdtr.base+0x10..gdtr.base+0x18 we'll see if there's anything wrong with the segment descriptor. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.