Re: [Xen-devel] [PATCH v2 03/25] arm/altp2m: Add struct vttbr.

[Julien Grall <julien.grall@xxxxxxx>]

On 06/08/2016 09:54, Sergej Proskurin wrote:
> Hi Julien,
Hello Sergej,

> On 08/04/2016 06:15 PM, Julien Grall wrote:
> > On 04/08/16 17:11, Sergej Proskurin wrote:
> > > > > > diff --git a/xen/include/asm-arm/processor.h
> > > > > > b/xen/include/asm-arm/processor.h
> > > > > > index 15bf890..f8ca18c 100644
> > > > > > --- a/xen/include/asm-arm/processor.h
> > > > > > +++ b/xen/include/asm-arm/processor.h
> > > > > > @@ -529,6 +529,22 @@ union hsr {
> > > > > >
> > > > > >
> > > > > >  };
> > > > > > +
> > > > > > +/* VTTBR: Virtualization Translation Table Base Register */
> > > > > > +struct vttbr {
> > > > > > +    union {
> > > > > > +        struct {
> > > > > > +            u64 baddr :40, /* variable res0: from 0-(x-1) bit */
> > > > > As mentioned on the previous series, this field is 48 bits for ARMv8
> > > > > (see ARM D7.2.102 in DDI 0487A.j).
> > > I must have missed it during refactoring. At this point, I will
> > > distinguish between __arm__ and __aarch64__, thank you.
> > After reading this series I see no point having this union. So I would
> > much prefer to see this patch dropped.
> I can do that. However, I do not understand why we would prefer using
> error prone bit operations for VTTBR initialization instead of having a
> unified and simple way of initializing and using the VTTBR including the
> VMID and the root table address.
The VTTBR only needs to be initialized in one place and we don't care 
accessing the fields. So I don't see the benefit to introduce a 
structure for that.
Regards,

--
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel