Re: [PATCH RFC] pvh: clearly specify used parameters in vcpu_guest_context

["Roger Pau Monné" <roger.pau@citrix.com>]

On 15/11/13 17:55, Tim Deegan wrote:
> At 16:32 +0000 on 15 Nov (1384529574), Jan Beulich wrote:
>>>>> On 15.11.13 at 16:50, Roger Pau Monne <roger.pau@citrix.com> wrote:
>>> --- a/xen/arch/x86/domain.c
>>> +++ b/xen/arch/x86/domain.c
>>> @@ -704,9 +704,11 @@ int arch_set_info_guest(
>>>          /* PVH 32bitfixme */
>>>          ASSERT(!compat);
>>>  
>>> -        if ( c(ctrlreg[1]) || c(ldt_base) || c(ldt_ents) ||
>>> +        if ( c(ctrlreg[0]) || c(ctrlreg[1]) || c(ctrlreg[2]) ||
>>> +             c(ctrlreg[4]) || c(ldt_base) || c(ldt_ents) ||
>>
>> I think it should actually be a bug for the guest to request an
>> all blank CR0 or CR4. Minimally CR0.PE, CR0.PG, and CR4.PAE
>> would seem to be a valid requirement to be set.
> 
> I think zero is better.  Guest CRx are explicitly _not_ loaded from 
> these fields so making them look like valid CRx values is just confusing.
> 
> But even better would be to allow all these fields to be set to any
> valid values, and to load the state into the guest vCPU.  I think
> that's going to be more sensible once the current restriction that PVH
> vCPUs are always in long more goes away.

Ack, I'm going to rework the patch in order to check and load the other
control registers.