Re: Restoring saved guest causes guest to reboot

[Markus Schade <markus.schade@gmail.com>]

On 05/24/2011 03:42 PM, Avi Kivity wrote:
> On 05/24/2011 04:37 PM, Markus Schade wrote:
>> On Tue, 24 May 2011, Avi Kivity wrote:
>>
>>>> Hmm, only 19 patches between .37 and .38 touch vmx.c. Avi, any idea
>>>> which
>>>> of those patches could cause this?
>>>
>>> Might be several.
>>>
>>> Markus, can you try a bisect?
>>>
>>> The command
>>>
>>> $ git bisect start v2.6.38 v2.6.37 arch/x86/kvm
>>>
>>> will generate test kernels for you to compile and run. There will be
>>> 7-8 tests needed, and most of the compiles should be short (esp. if
>>> you install ccache).
>>
>> Sure. I will take some time, though. Shall I use Linus git tree or the
>> kvm one?
>
> Either will work - the kvm tree includes the Linus tree. Since you
> tested .37 and .38, best to give those to git as starting points.

Git bisect tells me that this is the first bad commit:
-----------------%<-----------------
aff48baa34c033318ad322ecbf2e4bcd891b29ca is the first bad commit
commit aff48baa34c033318ad322ecbf2e4bcd891b29ca
Author: Avi Kivity <avi@redhat.com>
Date:   Sun Dec 5 18:56:11 2010 +0200

     KVM: Fetch guest cr3 from hardware on demand

     Instead of syncing the guest cr3 every exit, which is expensince on vmx
     with ept enabled, sync it only on demand.

     [sheng: fix incorrect cr3 seen by Windows XP]

     Signed-off-by: Sheng Yang <sheng@linux.intel.com>
     Signed-off-by: Avi Kivity <avi@redhat.com>

:040000 040000 fb059dc23facd323cafc88a39cff862f044d693d 
77247dfbfe49f0a732cbaa2593d794c3b6c8f0fc M      arch
-----------------%<-----------------

The full log is:

# bad: [521cb40b0c44418a4fd36dc633f575813d59a43d] Linux 2.6.38
# good: [3c0eee3fe6a3a1c745379547c7e7c904aa64f6d5] Linux 2.6.37
git bisect start 'v2.6.38' 'v2.6.37' 'arch/x86/kvm'
# good: [ec9e60b21977007e3dfacc2b8fe3a8fbb9276b51] KVM: X86: Introduce 
generic guest-mode representation
git bisect good ec9e60b21977007e3dfacc2b8fe3a8fbb9276b51
# good: [d4dbf470096c51cb4785167ea59fdbdea87ccbe4] KVM: MMU: Make the 
way of accessing lpage_info more generic
git bisect good d4dbf470096c51cb4785167ea59fdbdea87ccbe4
# good: [c445f8ef43bd9d2fb28213920d9b21f2465d22df] KVM: MMU: Initialize 
base_role for tdp mmus
git bisect good c445f8ef43bd9d2fb28213920d9b21f2465d22df
# bad: [444e863d13373b958ec6b133dcecf140d6c6c2ab] KVM: VMX: when 
entering real mode align segment base to 16 bytes
git bisect bad 444e863d13373b958ec6b133dcecf140d6c6c2ab
# good: [9f8fe5043fd26627c2fa2e9a41896885e675000b] KVM: Replace reads of 
vcpu->arch.cr3 by an accessor
git bisect good 9f8fe5043fd26627c2fa2e9a41896885e675000b
# bad: [b034cf0105235e65ee1b0161dbe8fef0338d06e7] KVM: MMU: audit: allow 
audit more guests at the same time
git bisect bad b034cf0105235e65ee1b0161dbe8fef0338d06e7
# bad: [aff48baa34c033318ad322ecbf2e4bcd891b29ca] KVM: Fetch guest cr3 
from hardware on demand
git bisect bad aff48baa34c033318ad322ecbf2e4bcd891b29ca

Best regards,
Markus