Re: Restoring saved guest causes guest to reboot

[Joerg Roedel <joro@8bytes.org>]

On Thu, May 26, 2011 at 05:20:32PM +0200, Markus Schade wrote:
> On 05/26/2011 01:28 PM, Markus Schade wrote:
>> On 05/26/2011 08:44 AM, Avi Kivity wrote:
>>> On 05/25/2011 09:49 AM, Markus Schade wrote:
>>>>
>>>> Git bisect tells me that this is the first bad commit:
>>>> -----------------%<-----------------
>>>> aff48baa34c033318ad322ecbf2e4bcd891b29ca is the first bad commit
>>>
>>> Does your machine have ept?
>>>
>>> (cat /sys/module/kvm_intel/parameters/ept)
>>>
>>
>> Sure. (Assuming that the Y means yes). I am no C developer, but I was
>> wondering, if the issue is related to the difference in
>> ept_update_paging_mode_cr0 between original patch in the kvm git and the
>> linux-2.6. git tree.
>
> I have re-added the missing 4 lines to ept_update_paging_mode_cr0 in  
> vmx.c, which resolves this issue for in Kernel 2.6,37 and 2.6.39.
> I haven't tested all guests, but neither Squeeze nor 2008 R2 reboot anymore.
>
> Markus
>
> static void vmx_set_efer(struct kvm_vcpu *vcpu, u64 efer)
> @@ -1921,6 +1940,8 @@
>                                         unsigned long cr0,
>                                         struct kvm_vcpu *vcpu)
>  {
> +       ulong cr3;
> +
>         vmx_decache_cr3(vcpu);
>         if (!(cr0 & X86_CR0_PG)) {
>                 /* From paging/starting to nonpaging */
> @@ -1936,8 +1957,11 @@
>                              vmcs_read32(CPU_BASED_VM_EXEC_CONTROL) &
>                              ~(CPU_BASED_CR3_LOAD_EXITING |
>                                CPU_BASED_CR3_STORE_EXITING));
> +               /* Must fetch cr3 before updating cr0 */
> +               cr3 = kvm_read_cr3(vcpu);
>                 vcpu->arch.cr0 = cr0;
>                 vmx_set_cr4(vcpu, kvm_read_cr4(vcpu));
> +               vmx_set_cr3(vcpu, cr3);

Hmm, not 100% sure, but the issue might be that the arch.cr3 value does
not make it into the vmcs after cr3 was changed from user-space? This
would also be fixed with the change above.

	Joerg