Re: [Xen-devel] [PATCH v2 07/16] x86: put XEN_DOMCTL_{set, get}_address_size under CONFIG_PV

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 31.10.18 at 10:33, <wei.liu2@xxxxxxxxxx> wrote:
> On Wed, Oct 31, 2018 at 03:00:17AM -0600, Jan Beulich wrote:
>> >>> On 30.10.18 at 21:50, <wei.liu2@xxxxxxxxxx> wrote:
>> > On Mon, Oct 29, 2018 at 08:28:07AM -0600, Jan Beulich wrote:
>> >> >>> On 19.10.18 at 16:28, <wei.liu2@xxxxxxxxxx> wrote:
>> >> > --- a/xen/arch/x86/domctl.c
>> >> > +++ b/xen/arch/x86/domctl.c
>> >> > @@ -608,6 +608,7 @@ long arch_do_domctl(
>> >> >              copyback = true;
>> >> >          break;
>> >> >  
>> >> > +#ifdef CONFIG_PV
>> >> >      case XEN_DOMCTL_set_address_size:
>> >> >          if ( ((domctl->u.address_size.size == 64) && 
>> >> > !d->arch.is_32bit_pv) ||
>> >> >               ((domctl->u.address_size.size == 32) && 
>> >> > d->arch.is_32bit_pv) )
>> >> > @@ -623,6 +624,7 @@ long arch_do_domctl(
>> >> >                                                                
>> >> > BITS_PER_LONG;
>> >> >          copyback = true;
>> >> >          break;
>> >> > +#endif
>> >> 
>> >> ... add such a check so that similar behavior will result with PV
>> >> enabled and disabled (error codes may differ, but success vs
>> >> error ought to match).
>> > 
>> > I don't follow. Do you mean adding is_pv_domain check somewhere?
>> 
>> Yes. Otherwise behavior differs between a PV and a !PV hypervisor.
> 
> I'm still at a loss to figure out what "similar behavior" you want. When
> you say behaviour differs, do you mean the lack of copyback in my patch?
> Why would that be relevant to a ENOSYS hypercall?

With !PV you'd get -ENOSYS (which is wrong in its own right, but
that a different topic). With PV you'd not get any error under at
least some conditions even for a HVM domain (if you don't make it
into switch_compat()), afaict.

Jan



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